Comment 3 for bug 1849334

Thanks for the branch, Chris! It does work in preventing staff from editing the precat owning library. However, there is a confusing feature in the UI: when staff attempt to modify the precat details in Item Status, they get the "Item(s) successfully modified toast", even though the items were not modified.

I wonder if the Perl code could throw an event if a staff member tries to edit an item with a call number with ID < 1, and then we could teach the AngularJS holdings editor to respect that event before sending the Broadcast channel (or it could send a failure notice along through the broadcast channel?). But that could also be split apart into its own separate bug.