Core bug related to Civi/Listener

When a change related to Case occurs Post hook gets called which inturn calls fireCaseChange function in Civi\CCase in which case updation takes place due to Civi/Listeners.
The same happens for deletion.

Therefore the delete api for Case ie api_v3_CaseTest.testCaseDelete used to break since the related Case is already deleted from the DB.
Hence skipping the update part when operation is delete.