message log: fix crash on exit

Author: jef-n

src/gui/qgsmessagelogviewer.cpp

@@ -60,6 +60,7 @@ QgsMessageLogViewer::QgsMessageLogViewer( QStatusBar *statusBar, QWidget *parent
     mButton->setCheckable( true );
     mButton->hide();
     connect( mButton, SIGNAL( toggled( bool ) ), this, SLOT( buttonToggled( bool ) ) );
+    connect( mButton, SIGNAL( destroyed() ), this, SLOT( buttonDestroyed() ) );
     statusBar->addPermanentWidget( mButton, 0 );
   }
 
@@ -100,6 +101,11 @@ void QgsMessageLogViewer::buttonToggled( bool checked )
     w->hide();
 }
 
+void QgsMessageLogViewer::buttonDestroyed()
+{
+  mButton = 0;
+}
+
 void QgsMessageLogViewer::logMessage( QString message, QString tag, int level )
 {
   mButton->setToolTip( tr( "%1 message(s) logged." ).arg( mCount++ ) );

src/gui/qgsmessagelogviewer.h

@@ -52,6 +52,7 @@ class GUI_EXPORT QgsMessageLogViewer: public QDialog, private Ui::QgsMessageLogV
   private slots:
     void closeTab( int index );
     void buttonToggled( bool checked );
+    void buttonDestroyed();
 };
 
 #endif