Unable to add pages when a vocabulary is set as required for pages

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 7.0.X, 7.1.X, Master
• Fix Version/s: 7.0.0 DXP FP64, 7.0.X, 7.1.0 M2, 7.1.X, Master
• Component/s: WCM > Categories, WCM > Sites Management > Pages Administration
• Labels:
  • QA-V
  • liferay-dxp-70-sp10
  • liferay-fixpack-de-64-7010
• Branch Version/s:
  7.0.x
• Backported to Branch:
  Committed
• Fix Priority: 3
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/56413

Steps to reproduce issue:

1. Navigate to Site Administration > Content > Categories
2. Add a vocabulary with the following configurations
   • Provide a name
   • Under "Choose Asset Type", select "Page"
   • Flag the "Required" toggle switch
3. Add a category to the vocabulary
4. Navigate to Site Administration > Navigation > Site Pages
5. Click [ + ] to select the page type
6. Select any page type
7. Provide a page name
8. Click "Submit"

Expected result:
Actual result: Page validation message displays, "An unexpected error occurred."

Reproduced on:
Tomcat 8.0.32 + MySQL 5.6
Portal master GIT ID: 63becb8353e57714bf179233e4b54ad73d6919b1