When plugging in a device with sensors that are unsupported by
iio-sensor-proxy, the proxy may quit so fast that the name disappears
from the bus before we get to construct the SensorProxy in response
to the name-appeared handler, resulting in the following warning:
JS ERROR: TypeError: this._sensorProxy is null
_sensorProxyAppeared/this._sensorProxy<@resource:///org/gnome/shell/misc/systemActions.js:217:17
_makeProxyWrapper/</<@resource:///org/gnome/gjs/modules/overrides/Gio.js:243:21
Address this by creating the proxy unconditionally instead of monitoring
the bus name, and using the g-name-owner property to determine whether
iio-sensor-proxy is active.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/1357
928b49705f