LibJS+LibWeb: Wrap raw JS::Cell*/& fields in GCPtr/NonnullGCPtr

Author: https://github.com/mattco98
Commit: 7c0c1c8f49
Pull-request: https://github.com/SerenityOS/serenity/pull/17743
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Runtime/FunctionEnvironment.h

@@ -52,7 +52,7 @@ private:
 
     Value m_this_value;                                                           // [[ThisValue]]
     ThisBindingStatus m_this_binding_status { ThisBindingStatus::Uninitialized }; // [[ThisBindingStatus]]
-    ECMAScriptFunctionObject* m_function_object { nullptr };                      // [[FunctionObject]]
+    GCPtr<ECMAScriptFunctionObject> m_function_object;                            // [[FunctionObject]]
     Value m_new_target { js_undefined() };                                        // [[NewTarget]]
 };