Vobsub: allow empty id language

Close #5525

modules/demux/vobsub.c

@@ -522,8 +522,16 @@ static int ParseVobSubIDX( demux_t *p_demux )
 
             /* Lets start a new track */
             if( sscanf( line, "id: %32[^ ,], index: %d",
-                        language, &i_track_id ) == 2 )
+                        language, &i_track_id ) != 2 )
             {
+                if( sscanf( line, "id: , index: %d", &i_track_id ) != 1 )
+                {
+                    msg_Warn( p_demux, "reading new track failed" );
+                    continue;
+                }
+                language[0] = '\0';
+            }
+
             p_sys->i_tracks++;
             p_sys->track = xrealloc( p_sys->track,
                     sizeof( vobsub_track_t ) * (p_sys->i_tracks + 1 ) );
@@ -550,11 +558,6 @@ static int ParseVobSubIDX( demux_t *p_demux )
             current_tk->p_es = es_out_Add( p_demux->out, &fmt );
             msg_Dbg( p_demux, "new vobsub track detected" );
         }
-            else
-            {
-                msg_Warn( p_demux, "reading new track failed" );
-            }
-        }
         else if( !strncmp( line, "timestamp:", 10 ) )
         {
             /*