Fix crash when reopening existing layouts

python/gui/layout/qgslayoutviewtoolselect.sip

@@ -25,6 +25,7 @@ class QgsLayoutViewToolSelect : QgsLayoutViewTool
 %Docstring
  Constructor for QgsLayoutViewToolSelect.
 %End
+    ~QgsLayoutViewToolSelect();
 
     virtual void layoutPressEvent( QgsLayoutViewMouseEvent *event );
 

src/app/layout/qgslayoutdesignerdialog.cpp

@@ -617,6 +617,7 @@ QgsLayout *QgsLayoutDesignerDialog::currentLayout()
 
 void QgsLayoutDesignerDialog::setCurrentLayout( QgsLayout *layout )
 {
+  layout->deselectAll();
   mLayout = layout;
   connect( mLayout, &QgsLayout::destroyed, this, &QgsLayoutDesignerDialog::close );
 

src/gui/layout/qgslayoutmousehandles.cpp

@@ -311,6 +311,9 @@ bool QgsLayoutMouseHandles::selectionRotation( double &rotation ) const
 
 double QgsLayoutMouseHandles::rectHandlerBorderTolerance()
 {
+  if ( !mView )
+    return 0;
+
   //calculate size for resize handles
   //get view scale factor
   double viewScaleFactor = mView->transform().m11();

src/gui/layout/qgslayoutviewtoolselect.cpp

@@ -30,6 +30,12 @@ QgsLayoutViewToolSelect::QgsLayoutViewToolSelect( QgsLayoutView *view )
   mRubberBand->setPen( QPen( QBrush( QColor( 254, 58, 29, 100 ) ), 0, Qt::DotLine ) );
 }
 
+QgsLayoutViewToolSelect::~QgsLayoutViewToolSelect()
+{
+  if ( mMouseHandles )
+    mMouseHandles->deleteLater();
+}
+
 void QgsLayoutViewToolSelect::layoutPressEvent( QgsLayoutViewMouseEvent *event )
 {
   if ( mMouseHandles->shouldBlockEvent( event ) )
@@ -276,6 +282,7 @@ QgsLayoutMouseHandles *QgsLayoutViewToolSelect::mouseHandles()
 void QgsLayoutViewToolSelect::setLayout( QgsLayout *layout )
 {
   // existing handles are owned by previous layout
+  mMouseHandles->deleteLater();
 
   //add mouse selection handles to layout, and initially hide
   mMouseHandles = new QgsLayoutMouseHandles( layout, view() );

src/gui/layout/qgslayoutviewtoolselect.h

@@ -40,6 +40,7 @@ class GUI_EXPORT QgsLayoutViewToolSelect : public QgsLayoutViewTool
      * Constructor for QgsLayoutViewToolSelect.
      */
     QgsLayoutViewToolSelect( QgsLayoutView *view SIP_TRANSFERTHIS );
+    ~QgsLayoutViewToolSelect();
 
     void layoutPressEvent( QgsLayoutViewMouseEvent *event ) override;
     void layoutMoveEvent( QgsLayoutViewMouseEvent *event ) override;