Bug: Cohorts fail to calculate or be deleted if referencing another deleted cohort

[darkopia]

Bug Description

Bug description

Please describe.
If a cohort is referencing another Cohort that has been deleted, it will fail to calculate (probably expected) but deleting it triggers a 500 error, its removed from the UI but reappears on a refresh.

If you are on PostHog Cloud it would be really valuable if you can share any links where the problem occurs. This speeds up our ability to troubleshoot tremendously.

How to reproduce

1. Create a cohort referencing another cohort
2. Delete the referenced cohort
3. Delete the referencing cohort.
4. Referencing cohort is deleted but reappears on refresh because of 500 error.

Additional context

Debug info