Issue Summary

When a user tries to use the @mention to reference another user, the list gets displayed further up on the UI.

This is reproducible on Data Center: (yes)

Steps to Reproduce

1. Login to a JSM instance and click on queues in the top left corner from the IT Service Desk project.
2. Select an issue => In the comment field, enter some text, then hit enter 20 times to create some room.
3. Try to mention a user by using @ and see the list displayed outside the comment field.

Expected Results

The list displayed when the user tries to reference another user by using @ should have been displayed within the comment field as shown below:

Actual Results

The list displayed after the user calls the @ in the comment field displays further up the UI as shown below:

The below exception is thrown in the xxxxxxx.log file:
No errors are displayed in the logs

Workaround

This issue does not happen when you open the ticket in a new tab via the issue key.