The login dialog has a maximum height set to prevent the user list
from growing indefinitively. However this approach fails if the
monitor height is smaller as said maximum, so add some additional
top/bottom padding to make sure there's some whitespace above/below
the user list in that case as well.
https://bugzilla.gnome.org/show_bug.cgi?id=685851
border: none;
background-color: transparent;
+ padding-bottom: 80px;
+ padding-top: 80px;
+
border-radius: 16px;
min-height: 150px;
max-height: 700px;