As after any program update you should reboot your system then the sidebar starts again.
You're right, BUT...:
- ...what if there's no program update, just virus definion updates, or maybe no updates at all (just check to see IF there are any updates).
- ...what if I don't want to reboot my system right after a program update, and I do it manually later?
- ...you can restart sidebar manually yourself, you don't have to restart
The fact is that the bug is present, and sidebar shouldn't be closed by Avast!