Steps to reproduce:

1. Open Host edit form
2. Add new value mapping
3. Inspect HTML and alter hidden input type value to something like "zzz"

Result:

Inline error is added after hidden input element.

Expected:
Same as 7.4: global error is displayed at the top of form. If there is actual case, that pop-up form could add row which would cause validation error, then an error container should be used to display error message.