Getting 500 error on deleting the card which doesn't have child

[SIVN1]

Describe the bug
If we try to delete the card which doesn't have child card throwing 500 error message

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Flyt application'
2. Create a process
3. Inside the process create the cards under main activity card
4. Try to delete any sub activity card or linked process card which doesn't have child card - Getting500 error

Expected behavior
We should be able to delete the card

Screenshots

CC: @AnjaliPandit20 @srvEq @ThomasBracho1987 @luan-droid

[SIVN1]

@MBanova @srvEq Verified in prod. Working fine. Able to delete the end nodes

Before deleting the card:

Delete pop up:

After deleting the card:

CC: @AnjaliPandit20 @ThomasBracho1987 @luan-droid