avformat: validate encoding of meta informations (fixes #8390)

(cherry picked from commit 17c4881762c30e3c966069318428ef292b8566f0)

modules/demux/avformat/demux.c

@@ -891,7 +891,7 @@ static int Control( demux_t *p_demux, int i_query, va_list args )
                     continue;
 
                 AVDictionaryEntry *e = av_dict_get( dict, names[i], NULL, 0 );
-                if( e != NULL && e->value != NULL )
+                if( e != NULL && e->value != NULL && IsUTF8(e->value) )
                     vlc_meta_Set( p_meta, i, e->value );
             }
             return VLC_SUCCESS;