When grading assignments unable to select annotation comment using the mouse

Environment:

1. It should be run in as many supported browsers as possible. At least:
   • Google Chrome 80.
   • MS Edge 44 (EdgeHTML 18).
   • Mozilla Firefox 74.
   • Internet Explorer 11
2. Ghostscript. If it's not installed, you can execute the following commands from the console: 

   $ apt-get update

   $ apt-get install ghostscript

Testing instructions:

1. Login as admin.
2. Access to "Site administration / Server / System paths", set "Path to ghostscript" to '/usr/bin/gs' or the corresponding to your environment and Save changes.
3. Check a green check is displayed near the "Path to ghostscript" field.
4. Access to "Site administration / Plugins / Activity modules / Assignment / Feedback plugins / Annotate PDF" and check "Annotate PDF" feedback plugin is enabled.
5. Create two students.
6. Create a course.
7. Create an assignment with Annotate PDF feedback ticked.
8. Enrol a student (yourself) into the course.
9. Login as the student and submit submission.
10. Login as a teacher and grade submission.
11. Add a multiline annotation comment.
12. With the `comments` tool selected, attempt to highlight the text in the annotation comment with a mouse.
13. Confirm, that it highlights the text rather than dragging around the assignment.