Ensure cyclic dependencies between scripts are broken at exit

modules/gdscript/gdscript.cpp

@@ -1053,7 +1053,9 @@ GDScript::~GDScript() {
 		memdelete(E->get());
 	}
 
-	GDScriptCache::remove_script(get_path());
+	if (GDScriptCache::singleton) { // Cache may have been already destroyed at engine shutdown.
+		GDScriptCache::remove_script(get_path());
+	}
 
 	_save_orphaned_subclasses();
 
@@ -2035,7 +2037,23 @@ GDScriptLanguage::~GDScriptLanguage() {
 	if (_call_stack) {
 		memdelete_arr(_call_stack);
 	}
-	singleton = nullptr;
+
+	// Clear dependencies between scripts, to ensure cyclic references are broken (to avoid leaks at exit).
+	while (script_list.first()) {
+		GDScript *script = script_list.first()->self();
+		for (Map<StringName, GDScriptFunction *>::Element *E = script->member_functions.front(); E; E = E->next()) {
+			GDScriptFunction *func = E->get();
+			for (int i = 0; i < func->argument_types.size(); i++) {
+				func->argument_types.write[i].script_type_ref = Ref<Script>();
+			}
+			func->return_type.script_type_ref = Ref<Script>();
+		}
+		for (Map<StringName, GDScript::MemberInfo>::Element *E = script->member_indices.front(); E; E = E->next()) {
+			E->get().data_type.script_type_ref = Ref<Script>();
+		}
+	}
+
+	singleton = NULL;
 }
 
 void GDScriptLanguage::add_orphan_subclass(const String &p_qualified_name, const ObjectID &p_subclass) {