Fix for issue 3427268 Crash when stopping playback

Change-Id: I4cd615ffa8c5db39ec34dc14f6b09fad55cae263
diff --git a/libvideoeditor/lvpp/VideoEditorPreviewController.h b/libvideoeditor/lvpp/VideoEditorPreviewController.h
index e9e4e84..c9d7de0 100755
--- a/libvideoeditor/lvpp/VideoEditorPreviewController.h
+++ b/libvideoeditor/lvpp/VideoEditorPreviewController.h
@@ -137,6 +137,7 @@
 

     M4VIFI_UInt8*  mFrameRGBBuffer;

     M4VIFI_UInt8*  mFrameYUVBuffer;

+    mutable Mutex mLockSem;

     static M4OSA_ERR preparePlayer(void* param, int playerInstance, int index);

     static M4OSA_ERR threadProc(M4OSA_Void* param);

     static void notify(void* cookie, int msg, int ext1, int ext2);