MR without CI cannot be accepted

Summary

A Merge Request on a branch without any CI (.gitlab-ci.yml) cannot be accepted through the gitlab interface.

Steps to reproduce

Simply create a new branch and delete the existing .gitlab-ci.yml.

We have a .gitlab-ci.yml on our master but we don't on our backport branches.

What is the current bug behavior?

The Merge button is disabled. Moreover, since there is no applicable pipeline, nor DevOps, the explanation is wrong.

What is the expected correct behavior?

The Merge button should be enabled, since no Pipeline should have been ran.

Relevant logs and/or screenshots

The Auto DevOps is disabled.

This was working up to 9.5.x (Gitlab CE) and we didn't change any settings during the upgrade to 10.0.