Wysiwyg editor makes the submit button unclickable when text or subject field is empty

[rich20]

Describe the bug
When the subject or text field is empty, the Wysiwyg editor makes the submit button unclickable.

To Reproduce
Open the console, create a new topic or reply and let a field (subject or text field) empty.Then click on submit.

Actual result
You see only in the console:
An invalid form control with name='message' is not focusable.

System information
Joomla version: 3.9.15-dev
Kunena version: 5.1.16-DEV
Php version: 7.3.11
Database version: 5.2.28

[github-actions]

This issue is stale because it has been open 30 days with no activity.