Should not create a custom master pages template named Blank

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: Master
• Fix Version/s: 7.3.0 CE GA1, 7.3.10 DXP GA1, Master
• Component/s: WCM
• Labels: None
• Fix Priority: 4
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/81930

Step to reproduce:

1. Create a custom master pages template:
   • Site Administration > Site Builder > Page Templates > Masters tab
   • Click add button.
2. Type name with Blank.
3. Click Save.

Expected Results:
The creation should not be succeeded. And there should be an alert message A page template entry with that name already exists.

Actual Results:
The custom master pages template named Blank is created successfully.

Reproduced on:
Tomcat 9.0.17 + MySQL 5.7. Portal master GIT ID: 7ce7ab20a3835fe3634c284e434a175a6dc0c95a.