Clicking "Merge Request" button on branches page should click through to open MR

Summary

Steps to reproduce

• Browse to a repo
• Click through to branches
• Click "Merge Request" on the 32393 branch

What is the current bug behavior?

The "new MR" form is shown.

What is the expected correct behavior?

The open MR, jamietanna/gitlab-test-repo!3 is opened.

Relevant logs and/or screenshots

N/A

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Found on GitLab.com, GitLab Enterprise Edition 9.2.2-ee b004167

Results of GitLab application Check

Found on GitLab.com, GitLab Enterprise Edition 9.2.2-ee b004167

Possible fixes

N/A