Merge pull request #91247 from AThousandShips/callable_fix

Fix unsafe uses of `Callable.is_null()`

editor/gui/editor_validation_panel.cpp

@@ -81,7 +81,7 @@ void EditorValidationPanel::set_update_callback(const Callable &p_callback) {
 }
 
 void EditorValidationPanel::update() {
-	ERR_FAIL_COND(update_callback.is_null());
+	ERR_FAIL_COND(!update_callback.is_valid());
 
 	if (pending_update) {
 		return;