File selector UI loading icon should show error for forbidden files

[HazelGrant]

Child ticket for #1571

Current behavior: If a user selects a forbidden file from the file selector, nothing happens. (After PR 3144 is merged, the loading icon will spin indefinitely until another file is selected.)

Expected behavior: Either files/directories that a user doesn't have permission to choose don't show up at all (more involved solution), or when a user clicks on a file/directory they don't have permission for, the UI shows that's why it isn't loading with an error message.