is_discharging bug fix for linux desktops (without batteries)

[pehses]

Previously, himawaripy.service failed to start since the is_discharging check could not find any batteries and then failed. An alternative would be to use an alternate himawaripy.service file for desktops that does not use the "--save_battery" flag.

[skyywj]

小严同学已收到您的邮件，