BusyCal's icon in the dock is not showing after the update

Dock needs to be force quit in order to reload the new icon

BusyCal was recently updated with a new icon, however after the update, Dock may continue to look for the old (non-existent) icon. To fix this, open Activity Monitor.app, search for "Dock", select it and click on the Force Quit button.

This will relaunch macOS Dock, causing it to reload the new icon.