Allow signal connecting even if script is invalid (only when compiled with tools), fixes #17070

modules/gdnative/pluginscript/pluginscript_script.h

@@ -102,6 +102,7 @@ public:
 	PropertyInfo get_property_info(const StringName &p_property) const;
 
 	bool is_tool() const { return _tool; }
+	bool is_valid() const { return true; }
 
 	virtual ScriptLanguage *get_language() const;