500 error code in component editor dialog trying to edit discarded component.

Scenario:

1. Login as admin and add banner component to some container.
2. Using another browser login as editor and go to edited by admin page.
3. As admin discard changes.
4. As editor click locked by admin edited banner.

Problem: Dialog with 500 error code. See attachment.
Expected: No dialog or site reloading with discarded changes. Need decision.