It should not be possible to unapprove or approve a merged MR

Using quick actions it is possible to both unapprove and approve an MR which has already been merged. Neither of these abilities seems logical to me. Further, this makes record keeping more complicated as it means the list of Approvals for a merged MR is not a static thing.

To reproduce:

• find a merged MR that you had approved
• enter a new comment with a quickaction /unapprove

Actual result:

• your approval is removed from the MR, and possibly the MR is listed as still needing approval

Expected result:

• neither the /approve nor /unapprove quickactions should be usable on a merged MR

Maybe this is by design for some reason but it seems like an oversight. At least the UI certainly does not seem to expose Approve/Unapprove buttons for merged MRs.