Clientside validation prompts for repo URL when disabling repository mirroring

Summary

When Remote mirror Repository is enabled and you want to disable it the clientside validation forces you to enter a valid SSH url even though the checkbox is not enabled

Gitlab version: 9.5.4-ee

Steps to reproduce

Go to Settings --> Repository --> Push to a remote repository Enable repository mirroring - click "Save changes"

Disable repository mirroring - click "Save changes".

Expected behaviour

Changes was saved.

Actual behaviour

Clientside validation prompts for a valid repository URL. Adding a valid SSH url makes CS validation happy and changes can be saved