The message port closed before a response was received

I’m getting The message port closed before a response was received. and also handling response: TypeError: Cannot read property 'loggedOut' of undefined in both a plugin I’m working on and now in this:

https://github.com/pfaffman/discourse-custom-homepage-for-groups/blob/main/common/head_tag.html

I guess it’s related to Upcoming core changes that may break some themes/components (April 12), but it’s not immediately clear just how.

EDIT: Well, I fixed the problems in my theme component (it works again and isn’t throwing errors), but I’m still seeing the above errors.