[BUGFIX] replace return of wrong error variable

[Denis-Kuso]

This fixes the issue #3012 where the error returned by the Notify() call would incorrectly return a nil value (from dbus.SessionBus()), instead of the correct non-nil value (from call.Err).

[Denis-Kuso]

I noticed that errors returned by the Notify function are ignored throughout
the codebase, perhaps indicating that notification failures aren’t considered
critical. Given this, I didn't add tests for the obj.Call error path,
as it doesn't seem necessary (nor is it currently tested) to propagate the
error or affect the application's flow. Let me know if you'd prefer otherwise.

[dominikschulz]

Thank you.

[dominikschulz]

I noticed that errors returned by the Notify function are ignored throughout the codebase, perhaps indicating that notification failures aren’t considered critical. Given this, I didn't add tests for the obj.Call error path, as it doesn't seem necessary (nor is it currently tested) to propagate the error or affect the application's flow. Let me know if you'd prefer otherwise.

Correct choice. For most instances I don't consider the returned errors from this method important since notifications are mostly best effort anyway. But I still think it's important that the method correctly returns errors - if any - so the callers can decide if and how to handle them.