Issue: In Custom Document type, when 'Required' set to No, still unable to make the fields blank in new document.
Steps to Reproduce
1. Navigate to Control Panel -> Click on Documents & Media -> Manage Document Types -> Click Add
2. Change Type Name to MyCustomDocument
3. In Main Meta Data Fields Drag and Drop Date Field
4. Click on Edit & Change Field Label to "Start Date" & Required to No
5. Drag and Drop Date Field - > Click on Edit & Change Field Label to "End Date" & Required to No
6. Click Save and Close the PopUp Window.
7. Click on Add -> MyCustomDocument - > You will see Start Date & End Date fields.
8. Unavle to select 'None' as the date. You can click the calendar icon, but the None button no longer exists.
Actual Result: You cannot make the fields blank. There is no way to leave it at None.
Intended Result: You can make the fields blank by selecting the Calendar Icon and clicking 'None' or selecting None from the drop down menu.