Add a debug assert relating to multiframe item crashes

src/core/layout/qgslayoutframe.cpp

@@ -163,6 +163,7 @@ void QgsLayoutFrame::draw( QgsRenderContext &context, const QStyleOptionGraphics
   {
     //calculate index of frame
     int frameIndex = mMultiFrame->frameIndex( this );
+    Q_ASSERT_X( frameIndex >= 0, "QgsLayoutFrame::draw", "Invalid frame index for frame" );
     mMultiFrame->render( context, mSection, frameIndex, itemStyle );
   }
 }

src/core/layout/qgslayoutitemattributetable.cpp

@@ -540,6 +540,7 @@ QgsExpressionContext QgsLayoutItemAttributeTable::createExpressionContext() cons
 
 void QgsLayoutItemAttributeTable::finalizeRestoreFromXml()
 {
+  QgsLayoutTable::finalizeRestoreFromXml();
   if ( !mMap && !mMapUuid.isEmpty() && mLayout )
   {
     mMap = qobject_cast< QgsLayoutItemMap *>( mLayout->itemByUuid( mMapUuid, true ) );

src/core/layout/qgslayoutmultiframe.cpp

@@ -54,7 +54,7 @@ double QgsLayoutMultiFrame::findNearbyPageBreak( double yPos )
 
 void QgsLayoutMultiFrame::addFrame( QgsLayoutFrame *frame, bool recalcFrameSizes )
 {
-  if ( !frame )
+  if ( !frame || mFrameItems.contains( frame ) )
     return;
 
   mFrameItems.push_back( frame );