Page's master page can revert back to default

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 7.3.X, Master
• Fix Version/s: 7.3.7 CE GA8, 7.3.10 DXP FP2, 7.3.X, 7.4.1 CE GA2, Master
• Component/s: Pages > Page Administration
• Labels:
  • ee-ts
  • liferay-fixpack-dxp-2-7310
• Branch Version/s:
  7.3.x
• Backported to Branch:
  Committed
• Fix Priority: 4
• Git Pull Request: https://github.com/liferay-echo/liferay-portal/pull/4509

Reproduction steps:

1. Design→Page Templates→Masters tab→ + sign
2. Add a new master page: TestMasterPage→Publish Master
3. Site Builder→Pages→Add a new page based on TestMasterPage, title: TestPage
4. Click on Publish
5. Edit the page
6. In the right menu, select the Page Design Options menu icon
7. Checkpoint: under the Master tab you see that TestMasterPage is selected
8. Click on the Configure button in the upper right corner→SEO
9. Enter test in the HTML Title field→Save
10. Edit the page again→Page Design Options menu icon→Master tab

Expected behaviour: TestMasterPage remains selected
Actual behaviour: Blank is selected