add comment about possible panic

src/hud.rs

@@ -1094,6 +1094,7 @@ fn handle_target_event(
             play_sfx = true;
         }
         if let Some(entity) = target {
+            // TODO: This can panic if the entity despawns in the meantime
             commands.entity(*entity).insert(IsTargeted);
             play_sfx = true;