Clear data in merge data when clearing diff3List

Without this resize events are sometimes sent before the stale
merge list has been removed leading to intermittent crashing.

src/mergeresultwindow.h

@@ -41,6 +41,12 @@ public:
       const Diff3LineList* pDiff3LineList,
       TotalDiffStatus* pTotalDiffStatus
       );
+
+   inline void clearMergeList()
+   {
+       m_mergeLineList.clear();
+   }
+
    void initActions(KActionCollection* ac);
    void reset();
 

src/pdiff.cpp

@@ -142,6 +142,8 @@ void KDiff3App::mainInit(TotalDiffStatus* pTotalDiffStatus, bool bLoadFiles, boo
     // so painting must be suppressed
     if(bGUI) setLockPainting(true);
 
+    //insure merge result window never has stale iterators.
+    if(m_pMergeResultWindow) m_pMergeResultWindow->clearMergeList();
     m_diff3LineList.clear();
     m_diff3LineVector.clear();