Space beneath the form attachment list

There seems to be some blank space beneath the form attachment list where the background of the page is visible:

The space disappears when the viewport is narrow enough:

I know that the modal classes used for the popup have different effects based on the viewport width, which makes me think that the additional space could be related to those classes.

What should be done about this space? Is it fine for it to remain, or should we try to remove it?