Changing language with opened Unexpected Errors dialog leads to Error 500

Prerequisites: User should be added in Administrators group to see Admin panel and plugins (Administration->Plugins)

1. Click "Configure" link for Kaptcha plugin
2. Clear all fields and click [Save]
3. Change language

Actual result: Error 500 is shown
Expected result: Language changes without errors

Note, that the same error appears if you click on Administration->Admin mode/Exit admin in 3rd step