Running react-sample in dx-core 6.2-SN or running hello-saas in staging

• Create new page and open any existing page -> See page render correctly
• Click to preview page -> See page render correctly in preview mode 
• Click to edit page -> See blank page
• Click to preview page -> See blank page

Problem: tag body now is empty after switching from preview to edit

Expectation: Should display page correctly when switching from preview page to edit page