~/.config/dwm: Fix status line for weird/broken battery state

.config/dwm/status.sh

charge_path="/sys/class/power_supply"
charge_full=`cat $charge_path/BAT0/energy_full`
charge_now=`cat $charge_path/BAT0/energy_now`
charge_rate=$(($charge_now * 100 / $charge_full ))
if [ -z "$charge_full" -o -z "$charge_now" ]; then
	charge_rate="?"
else
	charge_rate=$(($charge_now * 100 / $charge_full ))
fi
charge_icon=" "
if [ "$(cat $charge_path/AC/online)" -eq "1" ]; then
	charge_icon="⚡"