0005729: Crash during model validation (access violation while running checks)
Description
CaseTalk can crash with an access violation while it runs its model validation checks in the background. The crash occurs intermittently as checks complete, and appears related to timing when many checks run in parallel. It produces an error report and interrupts the validation run.
Fixed. Model validation could crash intermittently when many checks ran in parallel and one finished just as it was being cleaned up. The completion handler now safely handles that timing, so validation runs complete without the error.
