Broken Web GUI with TypeError: Cannot set properties of undefined (setting 'errors')

I’ve encountered this problem when administering Syncthing on a different computer by accessing the Web GUI remotely. I was just trying to unpause some folders, and suddenly everything broke down. Then, I started to encounter these error messages when touching any controls in the GUI, e.g. trying to pause or unpause a folder or add ignore patterns. Regardless of what I try, the GUI comes back to the state shown in the screenshot below. Syncthing itself seems to be running regardless as I am still able to access the logs.

Has anyone got any idea what may be going on here?

logbar.js:11 TypeError: Cannot set properties of undefined (setting 'errors')
    at syncthingController.js:399
    at Scope.$broadcast (angular.js:14908)
    at eventService.js:27
    at Array.forEach (<anonymous>)
    at successFn (eventService.js:23)
    at angular.js:9452
    at processQueue (angular.js:13337)
    at angular.js:13353
    at Scope.$eval (angular.js:14589)
    at Scope.$digest (angular.js:14405)

Looks like the GUI crashes trying to set an error notification (or possibly no-error status) on a folder which doesn’t exist in the GUI, maybe because it’s paused.

Does this qualify as a bug to report on GitHub? I can’t reproduce the problem though. It happened only once, and I eventually got rid of it by restarting Syncthing.

I don’t think this needs an issue (without a repro and considering significance). Given I have that ugly JS controller code of ours open anyway, I added a check there to handle a missing folder like in other event handlers: gui: Handle folder missing in model on error event by imsodin · Pull Request #8120 · syncthing/syncthing · GitHub