mkv: Remove an unneeded test.

modules/demux/mkv.cpp

@@ -1050,11 +1050,8 @@ public:
     virtual ~matroska_segment_c()
     {
         for( size_t i_track = 0; i_track < tracks.size(); i_track++ )
-        {
-            if ( tracks[i_track]->p_compression_data )
         {
             delete tracks[i_track]->p_compression_data;
-            }
             es_format_Clean( &tracks[i_track]->fmt );
             free( tracks[i_track]->p_extra_data );
             free( tracks[i_track]->psz_codec );