Exiting FullScreen from the gallery macro scrolls the page in a random location

The user is losing context of where it was when reading, since entering and leaving a gallery macro scrolls a bit the page upon exiting the full-screen. This affects a lot the reading experience, especially for Changes Report pages that contain multiple gallery macros.

Example Changes Report: https://www.xwiki.org/xwiki/bin/view/ReleaseNotes/Code/Report?action=report&displayer=grid&products=XWiki&versions=12.%25&categories=&audience=&importance=High%2CMedium&containsScreenshots=true