To reproduce:

• Go to the add release group page
• Enter a URL, e.g. http://example.com/ and select the "other databases" type
• Add another URL, e.g. http://en.wikipedia.org/wiki/Foo
• Press the submit button

Expected behaviour: It refuses to submit the edits because the first URL isn't allowed.
Actual behaviour: As long as you add a valid URL after the invalid one, it will re-enable the submit button and let you submit it anyway.