User Custom Attributes not updating from LDAP when field is blank

• Type: Regression Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 6.1.1 CE GA2, 6.1.20 EE GA2
• Fix Version/s: 6.1.30 EE GA3, 6.2.0 CE M4
• Component/s: Application Security > LDAP, Portal Configuration, Portal Configuration > Custom Fields
• Labels:
  • QA-R
  • QA-TP
• Branch Version/s:
  6.1.x
• Backported to Branch:
  Committed
• Story Points: 2
• Git Pull Request: https://github.com/hhuijser/liferay-portal/pull/1204

1. Setup LDAP via portal-ext.properties. (sample file attached)
2. Create a custom user mapping in Control Panel -> Custom Fields -> Users -> Edit. Configure the permissions so that everyone can see it, or the user can't see it.
3. Add that mapping and the corresponding LDAP attributes to the ldap.user.custom.mappings.0= in portal-ext.properties
4. Sign in with that user, and check in the user profile -> Custom Fields
5. Change the field in LDAP to be blank
6. Login with that user again and check Custom fields.

Expected Behavior: Custom Field value should be updated.
Actual: Value is not

This works properly in 6.1.20.