Approvers are removed from Merge Request (MR) when the approver provided another MR for that MR and when it gets merged

Summary

When a Merge Request MR1 is opened and one of the listed approvers for that MR1 makes a MR2 himself against that MR1, then after MR2 will be merged into MR1, the approver will be removed from the list of approvers and cannot be added any longer back to the list of approvers of MR1.

Steps to reproduce

1. Create a MR1
2. Add a few approvers to MR1, among them approver A1
3. Let A1 create a MR2 against MR1
4. Let the author of MR1 merge MR2 into MR1
5. A1 will is nit removed from the list of approvers. A1 cannot be readded again, A1 simply does not appear any longer in the search list for potential approvers.

Example Project

Not publicly available, it's private.

What is the current bug behavior?

Approvers are removed if their Merge Request has been merged into a Merge Request to be approved by them

What is the expected correct behavior?

Approvers are not removed

Relevant logs and/or screenshots

not available

Output of checks

This bug happens on GitLab.com