Can not change master of content page

• Type: Regression Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: Master
• Fix Version/s: 7.3.0 CE GA1, 7.3.1 CE GA2, 7.3.2 CE GA3, Master
• Component/s: ~[Archived] WCM
• Labels: None
• Fix Priority: 4
• Last Working Version:
  Master
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/83796

Step to reproduce:

1. Add a custom master
2. Add a content page based on Blank
3. Click Look and Feel tab in page editor sidebar
4. Click Change Master
5. Select custom master
6. Click Done
7. Click Save

Expected Results:
The successful message should be shown.

Actual Results:
The following warning message is shown. Error:Please enter a valid name.
Note: Only on content page, not on content page template and display page template.

Reproduced on:
Tomcat 9.0.17 + MySQL 5.7. Portal master GIT ID: 9186340b1cc62e11da6e041291e6c60114457bfd.