Pipelines shown as running for closed merge requests

Summary

If you close a merge request and then push to the branch that was merged the MR shows that the pipeline for that branch is running even though the new commits are not part of the MR.

Steps to reproduce

1. Create a merge from branch A to master containing commit A1
2. Merge it
3. Push commit A2 to branch

What is the current bug behavior?

The MR shows a pipeline running for A2 although it only contains A1

What is the expected correct behavior?

Closed MR shouldn't show pipelines further than it's last commit, it could hide bugs