Users with no Agile subscription unable to add or edit Epic links

Summary

JIRA projects using Epic Links without Agile subscription enabled are unable to add Epic links to issues, add issues to Epics, or remove Epic links from current issues.

Environment

JIRA 6.5-OD-07
JIRA Agile 6.7.6

Steps to Reproduce

1. Create Project > Select Project Type > JIRA Default Schemes.
2. In the new project, create an Epic.
3. On the new Epic, click + under Issues in Epic
4. Create a new issue, change type from Epic to Task.
5. Save. You will notice that it has not been added to the Epic.

Expected Results

• On an instance with Agile subscription, or previous to this update, you would be able to add Epic Links:
  
• Additionally, from the issue view, you would be able to add an issue to an Epic right from that screen when cicking + sign.
• Lastly, you would have been able to clear the Epic Link field and remove the link.

Actual Results

• View the task you created in Steps to Reproduce, and click Edit. Scroll down to Epic Link and you will see there's no way to add an Epic Link.

Notes

• See screenshots for comparison of the code when an instance is working vs. not working.
• This does work in releases prior to this release.

Workaround

Start a trial of JIRA Agile