Bugfix: KMail: Detach from message observation when destructing KMReaderWin

Signed-off-by: Luke Dashjr <luke-jr+git@utopios.org>
(cherry picked from commit e53303b929)

kmail/kmreaderwin.cpp

@@ -780,6 +780,9 @@ void KMReaderWin::slotCycleAttachmentStrategy() {
 //-----------------------------------------------------------------------------
 KMReaderWin::~KMReaderWin()
 {
+  if (message()) {
+    message()->detach( this );
+  }
   clearBodyPartMementos();
   delete mHtmlWriter; mHtmlWriter = 0;
   delete mCSSHelper;