Clicking and dragging elment on page on PR comments activates drag-n-drop for uploads

Issue Summary

This is reproducible on Data Center: yes

Steps to Reproduce

Only found to be an issue in Firefox

1. Go to a PR and choose Diff view
2. Add a new comment on a line and enter some text
3. Click and drag the tab "Commits"
4. Notice the line comment container changes to a blue background ready for a file to be dropped.
5. Release the drag
6. Notice the comment container background remains blue and the user can't enter text

Expected Results

Once the user releases the drag, the blue background should disappear and the user should be able to continue to write their comment

Actual Results

Once the user releases the drag, the blue background does NOT disapper and the user can't write in the comment editor

Workaround

The user needs to refresh the page to be able to write a comment.