Edit restricted page in Confluence as administrator (with Collaborative Editing enabled) resulted in a blank page.

This only happens after the administrator attempts to save or discard the changes of a restricted page.

How to Replicate

Scenario 1

1. Create a test page in Confluence
2. Insert some content on it and save the page.
3. Next, please edit the page and make some modifications to the initial content of the page.
4. Once you've done this, then reattempt to save the page.
5. This then resulted in blank page.

Scenario 2

1. Create a test page in Confluence
2. Insert some content on it and save the page.
3. Next, please edit the page and make some modifications to the initial content of the page.
4. Once you've done this, then attempt to discard the changes that you've made
5. This then resulted in blank page.

Workaround
Use a separate user account that does not have administrator access for editing.