Issue Summary

Users cannot delete PIs when PI had a milestone and that milestone was deleted.

Steps to Reproduce

There should be A PI in the system. PI should have a related milestone. Make sure the PI doesn't have any other related work.

1. Log in to the application
2. Select PI from the preconditions in the context menu
3. Navigate to the milestone grid
4. Delete the related milestone from the application
5. Navigate to the PI grid
6. Try to delete the PI

Expected Results

PI is deleted

Actual Results

PI is not deleted, users receive the warning message that there is still some related work.

Workaround

Currently, there is no workaround for this behavior, the only thing we can suggest is to mark the PI as Archived until the bug is fixed.