Don't dump/clean media library if it's not active

Bug spotted by Anthony Loiseau

src/playlist/engine.c

@@ -484,8 +484,9 @@ void playlist_LastLoop( playlist_t *p_playlist )
                                           p_playlist->pp_sds[0]->p_sd->psz_module );
     }
 
+    if( config_GetInt( p_playlist, "media-library" ) )
+    {
         playlist_MLDump( p_playlist );
-
         /* Because this recursive function decreases the
          * p_playlist->p_ml_category refcount, it may get deleted.
          * However we will delete the p_playlist->p_ml_category in the
@@ -495,6 +496,7 @@ void playlist_LastLoop( playlist_t *p_playlist )
         /* We don't need the media library anymore */
         /* Decref all subitems, and the given items */
         recursively_decref( p_playlist->p_ml_category );
+    }
 
     PL_LOCK;
     FOREACH_ARRAY( playlist_item_t *p_del, p_playlist->all_items )