Brief summary of the bug
In a group by variable report, disabling and enabling all tenants from the only added definition source, causes the group by selection to disappear.

Steps to reproduce:

• create the following report
  • View: process instance - count
  • Group by: variable: <any variable>
• open the edit definition source by clicking on the pen icon
• open the tenants' popover, disable and then re-enable all tenants
• close the definition edit popover

Actual result :
The group by section is not visible

Expected result:
The group by section is visible and a group by can be selected