Deleting Test step defects from the Execution defects table in the Execution details page, causes a NullPointerException

Description
A NPE occurs when trying to delete a Test step defect from the Execution defect table.
This issue doesn't occur when deleting the defect directly from the Test step.

How to reproduce

1. Access the Execution details page and create a new Test step defect
2. Go to the Execution defects table and delete the Defect associated with the test step
   

Actual result/Attachments

Expected result
Defect should be deleted correctly