It's not possible to remove all Test sets from edit issue

Description
When trying to edit an issue like Test type, It is not possible to empty the test set

Pre-conditions
Have a Test associated with one or more Test Sets

How to reproduce

1. Open the Test issue
2. Click the Edit button
3. Go to Test Set section
4. Remove all Associated Test Sets
5. Click Update button 

Actual result/Attachments
No Test Set is not removed

Expected result

The field should be empty

Version

• Tested in Jira 9.10.2
• Xray 7.4.1-j9