diff --git a/runtime/interpreter/src/expressions.rs b/runtime/interpreter/src/expressions.rs
index 6611d3e0..8f2a8282 100644
--- a/runtime/interpreter/src/expressions.rs
+++ b/runtime/interpreter/src/expressions.rs
@@ -258,7 +258,7 @@ impl AstVisitor for Interpreter {
             }
             Expression::Ask(ask) => {
                 let prompt_val = self.visit_expression(&ask.prompt)?;
-                let ask_fn = self.ctx.registry.lookup("ask").unwrap();
+                let ask_fn = self.ctx.registry.lookup("ask").ok_or_else(|| crate::RuntimeError::new(crate::RuntimeErrorKind::UndefinedVariable("ask".to_string()), None, None))?;
                 ask_fn.call(&mut self.ctx, vec![prompt_val])
             }
             Expression::Lambda(lambda) => {
diff --git a/runtime/interpreter/src/statements.rs b/runtime/interpreter/src/statements.rs
index f6e80545..303c54d6 100644
--- a/runtime/interpreter/src/statements.rs
+++ b/runtime/interpreter/src/statements.rs
@@ -169,7 +169,7 @@ impl Interpreter {
             }
             Statement::Say(say_stmt) => {
                 let val = self.visit_expression(&say_stmt.value)?;
-                let say_func = self.ctx.registry.lookup("say").unwrap();
+                let say_func = self.ctx.registry.lookup("say").ok_or_else(|| RuntimeError::new(RuntimeErrorKind::UndefinedVariable("say".to_string()), None, None))?;
                 say_func.call(&mut self.ctx, vec![val])?;
                 Ok(FlowSignal::Normal)
             }
@@ -241,7 +241,7 @@ impl Interpreter {
                                 })
                             }
                         }
-                        let arity = variant.payload.as_ref().unwrap().len();
+                        let arity = variant.payload.as_ref().map_or(0, |p| p.len());
                         entries.insert(
                             var_name.clone(),
                             RuntimeValue::Function(Rc::new(VariantConstructor {
diff --git a/runtime/native_runtime/src/lib.rs b/runtime/native_runtime/src/lib.rs
index 5c39d318..3d829fcc 100644
--- a/runtime/native_runtime/src/lib.rs
+++ b/runtime/native_runtime/src/lib.rs
@@ -201,6 +201,9 @@ pub unsafe extern "C" fn ts_free_value(val: *mut TsValue) {
         return;
     }
     let value = Box::from_raw(val);
+    if value.data.pointer.is_null() {
+        return;
+    }
     if value.tag == TsTag::String as u32 {
         let _ = Box::from_raw(value.data.pointer as *mut String);
     } else if value.tag == TsTag::List as u32 {
@@ -244,41 +247,65 @@ unsafe fn value_to_string(val: *mut TsValue) -> String {
     } else if v.tag == TsTag::Float as u32 {
         v.data.float.to_string()
     } else if v.tag == TsTag::String as u32 {
-        (*(v.data.pointer as *const String)).clone()
+        if v.data.pointer.is_null() {
+            "null".to_string()
+        } else {
+            (*(v.data.pointer as *const String)).clone()
+        }
     } else if v.tag == TsTag::List as u32 {
-        let list = &*(v.data.pointer as *const Vec<*mut TsValue>);
-        let mut parts = Vec::new();
-        for &item in list {
-            parts.push(value_to_string(item));
+        if v.data.pointer.is_null() {
+            "[]".to_string()
+        } else {
+            let list = &*(v.data.pointer as *const Vec<*mut TsValue>);
+            let mut parts = Vec::new();
+            for &item in list {
+                parts.push(value_to_string(item));
+            }
+            format!("[{}]", parts.join(", "))
         }
-        format!("[{}]", parts.join(", "))
     } else if v.tag == TsTag::Map as u32 {
-        let map = &*(v.data.pointer as *const HashMap<String, *mut TsValue>);
-        let mut parts = Vec::new();
-        for (k, &val) in map {
-            parts.push(format!("{}: {}", k, value_to_string(val)));
+        if v.data.pointer.is_null() {
+            "{}".to_string()
+        } else {
+            let map = &*(v.data.pointer as *const HashMap<String, *mut TsValue>);
+            let mut parts = Vec::new();
+            for (k, &val) in map {
+                parts.push(format!("{}: {}", k, value_to_string(val)));
+            }
+            format!("{{{}}}", parts.join(", "))
         }
-        format!("{{{}}}", parts.join(", "))
     } else if v.tag == TsTag::Struct as u32 {
-        let s = &*(v.data.pointer as *const TsStruct);
-        let mut parts = Vec::new();
-        for (k, &val) in &s.fields {
-            parts.push(format!("{}: {}", k, value_to_string(val)));
+        if v.data.pointer.is_null() {
+            "unknown struct".to_string()
+        } else {
+            let s = &*(v.data.pointer as *const TsStruct);
+            let mut parts = Vec::new();
+            for (k, &val) in &s.fields {
+                parts.push(format!("{}: {}", k, value_to_string(val)));
+            }
+            format!("{} {{{}}}", s.name, parts.join(", "))
         }
-        format!("{} {{{}}}", s.name, parts.join(", "))
     } else if v.tag == TsTag::Model as u32 {
-        let m = &*(v.data.pointer as *const TsModel);
-        let mut parts = Vec::new();
-        for (k, &val) in &m.fields {
-            parts.push(format!("{}: {}", k, value_to_string(val)));
+        if v.data.pointer.is_null() {
+            "unknown model".to_string()
+        } else {
+            let m = &*(v.data.pointer as *const TsModel);
+            let mut parts = Vec::new();
+            for (k, &val) in &m.fields {
+                parts.push(format!("{}: {}", k, value_to_string(val)));
+            }
+            format!("{} {{{}}}", m.name, parts.join(", "))
         }
-        format!("{} {{{}}}", m.name, parts.join(", "))
     } else if v.tag == TsTag::Enum as u32 {
-        let e = &*(v.data.pointer as *const TsEnum);
-        if e.value.is_null() {
-            format!("{}.{}", e.name, e.variant)
+        if v.data.pointer.is_null() {
+            "unknown enum".to_string()
         } else {
-            format!("{}.{}({})", e.name, e.variant, value_to_string(e.value))
+            let e = &*(v.data.pointer as *const TsEnum);
+            if e.value.is_null() {
+                format!("{}.{}", e.name, e.variant)
+            } else {
+                format!("{}.{}({})", e.name, e.variant, value_to_string(e.value))
+            }
         }
     } else {
         "unknown".to_string()
diff --git a/runtime/vm/src/executor.rs b/runtime/vm/src/executor.rs
index a800df31..90083e26 100644
--- a/runtime/vm/src/executor.rs
+++ b/runtime/vm/src/executor.rs
@@ -36,7 +36,7 @@ impl VM {
 
             if self.debugger.is_enabled() {
                 let current_func =
-                    &self.module.functions[self.frames.last().unwrap().function_idx as usize];
+                    &self.module.functions[self.frames.last().ok_or(crate::error::VMError::StackUnderflow)?.function_idx as usize];
                 self.debugger.trace_instruction(
                     current_func,
                     ip,
@@ -52,7 +52,7 @@ impl VM {
                 Opcode::LoadConst => {
                     if let Some(Operand::ConstantIndex(c_idx)) = inst_operands.first() {
                         let current_func = &self.module.functions
-                            [self.frames.last().unwrap().function_idx as usize];
+                            [self.frames.last().ok_or(crate::error::VMError::StackUnderflow)?.function_idx as usize];
                         let lit = current_func
                             .chunk
                             .constants
@@ -73,7 +73,7 @@ impl VM {
 
                 Opcode::LoadLocal => {
                     if let Some(Operand::LocalIndex(l_idx)) = inst_operands.first() {
-                        let bp = self.frames.last().unwrap().base_pointer;
+                        let bp = self.frames.last().ok_or(crate::error::VMError::StackUnderflow)?.base_pointer;
                         let val = self.stack.get(bp + *l_idx as usize)?;
                         self.stack.push(val.clone())?;
                     } else {
@@ -83,7 +83,7 @@ impl VM {
 
                 Opcode::StoreLocal => {
                     if let Some(Operand::LocalIndex(l_idx)) = inst_operands.first() {
-                        let bp = self.frames.last().unwrap().base_pointer;
+                        let bp = self.frames.last().ok_or(crate::error::VMError::StackUnderflow)?.base_pointer;
                         let val = self.stack.pop()?;
                         self.stack.set(bp + *l_idx as usize, val)?;
                     } else {
@@ -769,7 +769,7 @@ impl VM {
                 Opcode::FieldLoad => {
                     if let Some(Operand::ConstantIndex(c_idx)) = inst_operands.first() {
                         let current_func = &self.module.functions
-                            [self.frames.last().unwrap().function_idx as usize];
+                            [self.frames.last().ok_or(crate::error::VMError::StackUnderflow)?.function_idx as usize];
                         let lit = current_func
                             .chunk
                             .constants
@@ -827,7 +827,7 @@ impl VM {
                 Opcode::FieldStore => {
                     if let Some(Operand::ConstantIndex(c_idx)) = inst_operands.first() {
                         let current_func = &self.module.functions
-                            [self.frames.last().unwrap().function_idx as usize];
+                            [self.frames.last().ok_or(crate::error::VMError::StackUnderflow)?.function_idx as usize];
                         let lit = current_func
                             .chunk
                             .constants
diff --git a/tools/package-manager/src/lib.rs b/tools/package-manager/src/lib.rs
index 23abd98b..053c923a 100644
--- a/tools/package-manager/src/lib.rs
+++ b/tools/package-manager/src/lib.rs
@@ -431,18 +431,21 @@ impl DocExtractor {
                         let sym_name = raw_name
                             .split('(')
                             .next()
-                            .unwrap()
+                            .unwrap_or("")
                             .split('{')
                             .next()
-                            .unwrap()
+                            .unwrap_or("")
                             .split('=')
                             .next()
-                            .unwrap()
+                            .unwrap_or("")
                             .trim();
-                        items.push(DocItem {
-                            name: sym_name.to_string(),
-                            doc: active_doc.join("\n"),
-                        });
+
+                        if !sym_name.is_empty() {
+                            items.push(DocItem {
+                                name: sym_name.to_string(),
+                                doc: active_doc.join("\n"),
+                            });
+                        }
                     }
                     active_doc.clear();
                 }