The grey background behind ImageMap dialogue disappears

Steps to reproduce:

1. Open a Confluence page in two incognito tabs

2. Click Edit the page in both tabs

3. In the first tab select ImageMap macro (a pop up should be displayed)

4. In the second tab type something, wait for the autosave to happen

5. The first tab should have a blue pop up in the top right corner, click review changes

6. A screen with content comparison is displayed, click Discard

Expected result:
After discarding changes the grey dimmed background should be displayed

Actual result:
The grey background disappears, which makes it hard to determine if the pop up is actually on top of the page, or if it is a content.