SolidOS should not silently fail when unable to retrieve WebID during granting permission

SolidOS/Mashlib has a tab for each resource/container to modify its sharing permissions / access control lists. It allows to grant permission to an individual WebID entered by the user.
If everything goes normal, after entering WebID and clicking yes, the textbox and yes/no disappears, and an avatar corresponding to that WebID will appear as a "viewer". Then the user can drag-and-drop it to the appropriate location.

However, if the entered WebID cannot be retrieved, the textbox and yes/no disappears as well, but nothing further happens. This is very un-user-friendly...

Preferably, SolidOS should either:

1. Alarm the user that something wrong happened when retrieving the WebID document; or
2. Add the WebID as a viewer regardlessly; or
3. A combination of the two above (e.g. alarm, and allow proceeding regardlessly).

I haven't tried similar things on other types, but maybe worth checking if they have similar issues?

Start in SolidOS/Mashlib's resource or container permission tab and reproduce the flow for entering a WebID that cannot be retrieved. Trace what happens after the user confirms the WebID, then determine whether the completed behavior should show an error, retain the WebID as a viewer, or do both. Done means the failed retrieval no longer leaves the interface silently unchanged.