AcceptDialog: fix child w/ ANCHOR_END sized wrong until resized

scene/gui/dialogs.cpp

@@ -357,6 +357,9 @@ void AcceptDialog::_notification(int p_what) {
 	if (p_what == NOTIFICATION_MODAL_CLOSE) {
 
 		cancel_pressed();
+	} else if (p_what == NOTIFICATION_READY) {
+
+		_update_child_rects();
 	} else if (p_what == NOTIFICATION_RESIZED) {
 
 		_update_child_rects();