The "is empty string" operator in a UI Policy may not work as expected

In a UI Policy, the "Is empty string" operator may not work as expected, as opposed to the "is empty" operator.

 

 

1. Navigate to Incident > Create New.
2. Right-click on the header bar and select Configure > All.
3. Go to the UI Policies section or tab.
4. Click New.
5. In Short Description, add text.
6. In When to Apply, set any string field to Is empty.
7. Right-click in the header bar and select Save. 
8. In the UI Policy Actions section or tab, click New.
9. Add a condition for any field.
   For example, set the Knowledge field to read only.
10. Click Submit.
11. Navigate to Incident > Create New. 
12. Create a new incident.
    The UI Policy is not applied.

This is expected behaviour. Unless it is set with a script, a field should not contain the empty string. We use null for fields that have no value, which the operator "is empty" will match. Use "is empty" instead. The operator "is empty string" is designed to do something different from comparing with null.