Closure Code - An Error has Occurred

Closure Code - An Error has Occurred

When a technician changes a request to closed and the closure code pop-up appears if they do not fill anything in we get presented with the attached error.

There should be a quick way of editing the closure codes (or I cannot find it) other than changing the request status back to open and then closed again.

Trying the above still closes the job but the error appears anyway.