Index: /trunk/src/VBox/Main/src-client/WebMWriter.cpp
===================================================================
--- /trunk/src/VBox/Main/src-client/WebMWriter.cpp	(revision 74780)
+++ /trunk/src/VBox/Main/src-client/WebMWriter.cpp	(revision 74781)
@@ -148,10 +148,13 @@
 
     WebMTracks::iterator itTrack = CurSeg.mapTracks.begin();
-    for (; itTrack != CurSeg.mapTracks.end(); ++itTrack)
+    while (itTrack != CurSeg.mapTracks.end())
     {
         WebMTrack *pTrack = itTrack->second;
-
-        delete pTrack;
+        if (pTrack) /* Paranoia. */
+            delete pTrack;
+
         CurSeg.mapTracks.erase(itTrack);
+
+        itTrack = CurSeg.mapTracks.begin();
     }