fix uncatched error with missing polkit. Closes: #5955

Well, exception is indeed technichally catched in backend, then converted into a signal, that is catched in the eip_status widget in the frontend, and converted into a signal to abort the connection that is sent to the backend again.

What I mean is that the whole exception catching should be done in the backend, without the ping-pong to the frontend, and without adding any logical checks in the frontend. We should just communicate UI changes to frontend, and abstract us away from anything else.