[C2] mail_notify_* extra fields have broken "possible values" after install

[ywarnier]

[christianbeeznest]

It is fixed in this PR #6140

Thanks for confirmation.

[ywarnier]

This is better. However, still for the same mail_notify_invitation field, for example, when I click Edit extra field options, I can see that the "Value" column is empty. When I edit the second option ("At once"), the "Value" input is empty and is... not an input.

I think the form itself is correct (you shouldn't be able to change the value of an option afterwards, just how it appears), but there must be something wrong at installation that adds the option "At once" but leaves its value empty.