Error is displayed when expanding a valid file diff

Summary

GitLab EE 10.5.1. When clicking, This diff is collapsed. Click to expand it., an error is displayed at the top of the screen even though the diff properly loads.

Steps to reproduce

Sample issue where the bug can be seen: https://gitlab.com/gitlab-org/gitlab-ee/commit/298dad2b55a7f76627dc3e0b2db796b7cdb6f3b0

What is the current bug behavior?

The following is shown when Click to expand it is executed.

Screen_Shot_2018-02-23_at_11.30.25_AM

Output of checks

This bug happens on GitLab.com and on local installs.