Quay can't enable Mirror for image repository

Description:

This is an issue found when configuring a private image repository to mirror status, after configuring the repository's Repository State to mirror,  go to Mirroring tab, fill required configurations of external registry, button "enable mirror" is gray and not clickable. see screenshot

Quay Image: quay.io/projectquay/quay:40cb9ed5

Steps:

1. Login Quay Console
2. Create new Private repository
3. Go to Repository settings tab, change "Repository State" to Mirror
4. Go to Repository Mirroring tab, provide required configurations of external registry
5. Click button "enable mirror"

Expected Results:

should be able to click button "enable mirror"

Actual Results:

Button "enable mirror" is gray and not clickable.