avformat/mxfdec: fix typo in error check of mxf_edit_unit_absolute_offset()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mxfdec.c

@@ -2540,7 +2540,7 @@ static int mxf_read_seek(AVFormatContext *s, int stream_index, int64_t sample_ti
             sample_time = FFMIN(sample_time, source_track->original_duration - 1);
         }
 
-        if ((ret = mxf_edit_unit_absolute_offset(mxf, t, sample_time, &sample_time, &seekpos, 1)) << 0)
+        if ((ret = mxf_edit_unit_absolute_offset(mxf, t, sample_time, &sample_time, &seekpos, 1)) < 0)
             return ret;
 
         ff_update_cur_dts(s, st, sample_time);