Steps to reproduce:

1. Open -> Alerts -> Media types
2. Select one of the Webbhooks, for Example Discord
3. Observe, that "Menu entry URL" field is enabled, although "Include event menu entry" is unchecked

Result:
The Menu entry URL field is enbaled, it is possible to type value (no inline validation in this case), and save the webhook. No URL will be added as result.
See video:

Expected:
"Menu entry URL" should be disabled, while "Include event menu entry" is unchecked.