QmlDesigner: Do not amend if rewriter view is not attached

Task-number: QDS-7349
Change-Id: I6a4d1906ee6afea25e5dcc878f7f502456c6052b
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/designercore/model/rewriterview.cpp

@@ -88,6 +88,7 @@ RewriterView::RewriterView(DifferenceHandling differenceHandling, QObject *paren
         m_textToModelMerger(new Internal::TextToModelMerger(this))
 {
     m_amendTimer.setSingleShot(true);
+
     m_amendTimer.setInterval(800);
     connect(&m_amendTimer, &QTimer::timeout, this, &RewriterView::amendQmlText);
 
@@ -535,6 +536,10 @@ void RewriterView::applyChanges()
 
 void RewriterView::amendQmlText()
 {
+
+    if (!model()->rewriterView())
+        return;
+
     emitCustomNotification(StartRewriterAmend);
 
     const QString newQmlText = m_textModifier->text();