daemon: Make sure power level is still critical before running critical battery action

This fixes an edge case where the critical battery timer could still trigger the action even if the battery was charged while in sleep.

Currently the logic only cancels the critical battery action if the computer is plugged in.

I found this bug when I closed the lid of my laptop after the critical battery notification appeared. I charged it for a few hours and then unplugged it. When I opened the lid again, the critical battery timer still put my computer to sleep.

Just a minor annoyance, but I thought I might as well fix it.

The only thing I added was a check to see if the battery level is still critical before running the critical battery action.