Fix a crash in live555 demuxer on close.

We must first close the stream before deleting the tracks, because tracks can be used in StreamClose callback.
This crash could only happen in recents version of live555 library.

modules/demux/live555.cpp

@@ -427,9 +427,13 @@ static void Close( vlc_object_t *p_this )
 {
     demux_t *p_demux = (demux_t*)p_this;
     demux_sys_t *p_sys = p_demux->p_sys;
-    int i;
 
-    for( i = 0; i < p_sys->i_track; i++ )
+    if( p_sys->rtsp && p_sys->ms ) p_sys->rtsp->teardownMediaSession( *p_sys->ms );
+    if( p_sys->ms ) Medium::close( p_sys->ms );
+    if( p_sys->rtsp ) RTSPClient::close( p_sys->rtsp );
+    if( p_sys->env ) p_sys->env->reclaim();
+
+    for( int i = 0; i < p_sys->i_track; i++ )
     {
         live_track_t *tk = p_sys->track[i];
 
@@ -441,16 +445,12 @@ static void Close( vlc_object_t *p_this )
 
     if( p_sys->i_track ) free( p_sys->track );
     if( p_sys->p_out_asf ) stream_Delete( p_sys->p_out_asf );
-    if( p_sys->rtsp && p_sys->ms ) p_sys->rtsp->teardownMediaSession( *p_sys->ms );
     if( p_sys->p_timeout )
     {
         vlc_cancel( p_sys->p_timeout->handle );
         vlc_join( p_sys->p_timeout->handle, NULL );
         free( p_sys->p_timeout );
     }
-    if( p_sys->ms ) Medium::close( p_sys->ms );
-    if( p_sys->rtsp ) RTSPClient::close( p_sys->rtsp );
-    if( p_sys->env ) p_sys->env->reclaim();
     delete p_sys->scheduler;
     free( p_sys->p_sdp );
     free( p_sys->psz_path );