"Compare changes" dropdown in merge request comments not rendering content

Summary

The "compare changes" dropdown functionality in merge request comments is not working properly. When code is modified at the location of a comment, clicking the dropdown fails to render any content. The only visible change is that the indicator symbol flips between up and down symbols.

Steps to reproduce

1. Create a merge request with code changes
2. Add a comment on a specific line of code
3. Make additional changes to the code at the location of the comment
4. When the "compare changes" dropdown appears next to the comment, click on it
5. Observe that no content is rendered, only the indicator symbol changes

Expected behavior

Clicking the "compare changes" dropdown should display the differences between the versions of code at the comment location, showing what has changed since the comment was made.

Environment

• GitLab version: 18.0.1

Additional information

Note that this also seems to affect rendering changes in the MR description. I've had a few developers I support bring this up as an issue affecting their workflow.

This issue description was created with the assistance of AI.