In some cases, clicking a button can fire its click handler twice.

This is likely related to the ng-submit + ng-click pattern that we use to enable using the "Enter" key to submit forms.

Steps to reproduce:

1. Open webserver logs
2. Navigate to Sign In page
3. Click "Sign In" without entering any credentials
   • Expected output: You should see 2 messages - one stating there was an error, and another containing the error itself
   • You will see 4 messages, each one of the above is produced twice

This ticket is complete when we have tracked down why this is happening, and mitigated it where possible.