Fix potential missing unlock (cid #1049392)

modules/video_filter/puzzle.c

@@ -453,8 +453,11 @@ picture_t *Filter( filter_t *p_filter, picture_t *p_pic_in ) {
             && p_sys->s_current_param.b_advanced ) {
         i_ret = puzzle_sort_layers( p_filter);
         if (i_ret != VLC_SUCCESS)
+        {
+            vlc_mutex_unlock( &p_sys->pce_lock );
             return CopyInfoAndRelease( p_pic_out, p_pic_in );
         }
+    }
 
     for (uint32_t i = 0; i < __MAX( 4, p_sys->s_allocated.i_pieces_nbr / 24 )
                             && ( !p_sys->b_bake_request && !p_sys->b_mouse_drag