Warn about funcref creation

modules/gdscript/gdscript_function.cpp

@@ -605,7 +605,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 #ifdef DEBUG_ENABLED
 				if (!valid) {
 					if (src->has_method(*index)) {
-						err_text = "Invalid get index '" + index->operator String() + "' (on base: '" + _get_var_type(src) + "'). Did you mean '." + index->operator String() + "()' ?";
+						err_text = "Invalid get index '" + index->operator String() + "' (on base: '" + _get_var_type(src) + "'). Did you mean '." + index->operator String() + "()' or funcref(obj, \"" + index->operator String() + "\") ?";
 					} else {
 						err_text = "Invalid get index '" + index->operator String() + "' (on base: '" + _get_var_type(src) + "').";
 					}