If that what works, you should use it, but it’s not really addressing the problem.
That div element is not normally given a specific height by the Field Group Tabs code. This is so it can expand to contain it’s content, which is going to be different for each tab.
So, it looks to me that some other javascript is setting the height of that div. If you can’t find what is doing that (that may be difficult to do), then you may have to resort to your fix, but you’ll find it doesn’t work very well because of the different heights of each tab’s content.
You may find that CSS that basically nullifies the height set by some other script works better, also using a selector that will get all the tabs with a single rule…something like this:
.pdb-admin-edit-participant .field-group {
height: inherit !important;
}
Participants Database has a place in the Custom CSS settings where you can put CSS that is active in the admin.