Fix crash in QQmlApplicationEngine when loading finishes

Task-number: QTBUG-30997

Change-Id: I10cb2c689408d1b31360095c2aa9e0943a5d9452
Reviewed-by: Alan Alpert <aalpert@blackberry.com>

src/qml/qml/qqmlapplicationengine.cpp

@@ -133,7 +133,8 @@ void QQmlApplicationEnginePrivate::_q_finishLoad(QObject *o)
     case QQmlComponent::Null:
         return; //These cases just wait for the next status update
     }
-    delete c;
+
+    c->deleteLater();
 }
 
 /*!