Unlinking a resource in a selection list doesn't immediately remove it from the on-screen list. #346

Whenever I unlink a resource from a selection list, it gets removed immediately in the database data, but it doesn't get removed from the list displayed in the manager. If I try to remove it again, I get an error, because it's actually not in that selection list any more, even though it looks like it is. Reloading the window doesn't remove it either; I have to clear the site cache and then reload for the linked resource to not show up in the list.

MODX 2.8.3-pl Collections 3.7.1-pl

I opened an issue for this in 2018, and it was supposed fixed, but it's not.
#258