* fix: check dbus response for nullptr before using
* chore: use BindOnce for ProxyObject::CallMethod cb
* chore: comment out name of unused argument
* fix: re-enable and fix linux power monitor tests
* fix: change tyop from code comments
* refactor: don't keep unnecessary dbus pointer
* chore: remove the 'TODO: fix this' spec comment
The event is emitted when the OS is rebooting/shutting down, and allows
an electron app to call `e.preventDefault()` in order to delay shutdown
and exit cleanly.