Description
Error is displaying under cases tab after upgrade from 7.11.1 to 7.12.0

Build Details:

Version: 7.12.0 BC2
Build: 39000
Commit: 4f65a5a1268fa78f1af9117d12312e1cee433376
Artifacts: https://staging.elastic.co/7.12.0-37f40745/summary-7.12.0.html

Browser Details:
All

Preconditions:

1. 7.11.1 Environment should exist.
2. Endpoint security should be installed.
3. Cases should be created with connectors.

Steps to Reproduce:

1. Upgrade the build from 7.11.1 to 7.12.0
2. Navigate to the cases tab
3. Observe that no cases are displayed. Moreover, error is displayed: 'Error fetching data'

Impacted Test case:
N/A

Actual Result:
Error is displaying under cases tab after upgrade from 7.11.1 to 7.12.0 build

Expected Result:
Cases should be displayed under the cases tab after upgrade from 7.11.1 to 7.12.0 build

What's working:
N/A

What's not working:
N/A

Screenshot: