Description of problem:
Found in test ServerSettingsTest.java

If the user sets the Server URL in Administration->Server Config, it cannot be set to default/anything else

Version-Release number of selected component (if applicable):
3.6

How reproducible:
Easy always

Steps to Reproduce:
1. Sign in as admin (with accessible email address), go to Administration -> Server Configuration
2. Set the server url to something like http://www.example.com and Save
3. Go back into Configuration, set it to "" (empty) and Save
4. Click Contact Admin in the footer
5. Send the filled in form
6. Check email (or mspool, if desired)

Actual results:
Server location is http://www.example.com

Expected results:
Server location is deriver (e.g. localhost etc)

Additional info: