Replying to MB post with a space generates a post with the title in its content

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: Master
• Fix Version/s: 7.1.X, Master
• Component/s: Message Boards
• Labels:
  • 7.1-could
  • INACTIVE
  • liferay-fixpack-dxp-1-7110
• Branch Version/s:
  7.1.x
• Backported to Branch:
  Committed
• Fix Priority: 3
• Sprint: 007 - Squirtle
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/61326

Steps to reproduce:

1. Add a MB thread
2. Reply to thread
3. In the text editor, hit the spacebar once (the reply will be blank if there are multiple spaces)
4. Publish the reply

Expected result:
Reply with no content is posted

Actual result:
Reply with RE: ${MB thread title} in the content field is posted.

Reproduced on:
Tomcat 9.0.6 + MySQL 5.6.
Portal master GIT ID: d596147e9d17cc9a809208584124df7849ad0c60