Avoid g_critical() errors when unable to connect to upower
This removes two g_critical() errors that are seen when running the tests in CI.
Before:
(tracker-miner-fs:7050): libupower-glib-WARNING **: 14:31:50.109: Couldn't connect to proxy: Could not connect: No such file or directory
(tracker-miner-fs:7050): GLib-GObject-CRITICAL **: 14:31:50.109: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
(tracker-miner-fs:7050): GLib-GObject-CRITICAL **: 14:31:50.109: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
** (tracker-miner-fs:7050): WARNING **: 14:31:50.109: Unable to connect to UPower
After:
(tracker-miner-fs:12620): libupower-glib-WARNING **: 14:38:52.337: Couldn't connect to proxy: Could not connect: No such file or directory
** (tracker-miner-fs:12620): WARNING **: 14:38:52.337: Unable to connect to UPower
Fixes #75 (closed)