Wrong attachment box size in attachment gallery picker when increasing body font size

Steps to reproduce

• Set body font size to 18px instead of 12px by default
• Edit home page and open gallery attachment picker dialog
• Search for "icon" in all pages

Actual result

When clicking on an attachment box, the highlighted box intersects with the box above and with the attachment caption:

With images having larger dimensions, the caption directly overlaps with the box in the next row, as illustrated by the capture below which uses images contained in the Masonry macro.