"Add" button in comments is greyed out when an attachment is added to the comments

Issue Summary

When an attachment is added in the comments (in text, not visual mode), the "Add" button is greyed out unless a 'Space' or some character is added on the comment box.

This is reproducible on Data Center: Yes

Affected on ,9.0, 9.1.0 . This is not observed in versions 8.22,8.20 

Steps to Reproduce

1. On Jira 9.1, Created a new issue
2. Add an image to the comment (New attachment or an existing attachment) 
3. The add button will greyed out and will be enabled if a character is added on the comment box. 

Expected Results

Actual Results

Workaround

Adding a character on the comment and removing them enables the Add button