Fix another crash with playlists. MTP playlist this time.

BUG: 297816
FIXED-IN: 2.6

ChangeLog

@@ -7,7 +7,7 @@ VERSION 2.6
 
   BUGFIXES:
     * Fix problems when sql server is not reachable (BR 298425)
-    * Fix crash with exporting playlists with invalid tracks (BR 303056 and BR 302607)
+    * Fix crash with exporting playlists with invalid tracks (BR 303056 and BR 302607 and BR 297816)
 
 VERSION 2.6-RC
   CHANGES:

src/core-impl/collections/mtpcollection/handler/MtpHandler.cpp

@@ -866,6 +866,8 @@ MtpHandler::libSavePlaylist( const Playlists::MediaDevicePlaylistPtr &playlist,
         uint32_t i = 0;
         foreach( Meta::TrackPtr trk, tracklist )
         {
+            if( !trk ) // playlists might contain invalid tracks. see BUG: 297816
+                continue;
             Meta::MediaDeviceTrackPtr track = Meta::MediaDeviceTrackPtr::staticCast( trk );
             tracks[i] = m_mtpTrackHash.value( track )->item_id;
         }