Fix FTBFS with GCC6

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit e5bb2c603d)

src/videopreview.cpp

@@ -221,7 +221,7 @@ TQPixmap VideoPreview::getFrame(const TQString &path, int flags)
     mplayerprocess->setArguments( args);
     mplayerprocess->start();
     while (mplayerprocess->isRunning() ) usleep (10);
-    if (tmpdir->qDir()->entryList( "*.jpg" ).isEmpty() ) return false;
+    if (tmpdir->qDir()->entryList( "*.jpg" ).isEmpty() ) return 0;
 
     TQString lastframe=tmpdir->qDir()->entryList( "*.jpg" ).last();
     kdDebug() << "videopreview: LastFrame==" << lastframe << endl;