Selection bar hidden behind navigation sidebar

[richardolsson]

Description

The selection bar is too wide when the nav bar is expanded, causing it to be partially hidden by the nav menu.

Steps to reproduce

1. Go to http://app.dev.zetkin.org/organize/1/projects/1/calendar?focusDate=2023-05-29&timeScale=week
2. Make sure the left-hand-side nav menu is open or expand it now
3. Hover any event and click the checkbox to select it

Expected Behaviour

Selection bar should appear along the bottom edge of the window, and be wide enough to cover most of the calendar, but no wider than that.

Actual Behaviour

The bar appears too wide, and extends behind the nav bar and outside the browser window on the right hand side.

Screenshots (if you have any)