Gaps in sidebar are inconsistent

[st3iny]

Steps to reproduce

1. Open the Calendar app.
2. Observe the gaps between the header, the calendar/appointment list and the bottom section of the left sidebar.

Expected behavior

The gaps should be consistent.

Actual behaviour

The top gap is a bit too small and the bottom gap is a bit too big. This gets more obvious when the sidebar has a scrollbar.

No overflow	With overflow (scroll)

Calendar app version

main