vobsub.c: Don't break autodetection of non-vobsub subtitles

modules/demux/vobsub.c

@@ -122,14 +122,14 @@ static int Open ( vlc_object_t *p_this )
         {
             msg_Dbg( p_demux, "this doesn't seem to be a vobsub file" );
             free( s );
-            return VLC_EGENERIC;
-        }
-        free( s );
-
             if( stream_Seek( p_demux->s, 0 ) )
             {
                 msg_Warn( p_demux, "failed to rewind" );
             }
+            return VLC_EGENERIC;
+        }
+        free( s );
+
     }
     else
     {