Reload the view if a previously unmounted device is mounted again

Reload the view if a previously unmounted device is mounted again

The problem was that DolphinViewContainer::setUrl(newUrl) was ignored
if newUrl is equal to the URL which is shown in the view already.

The new approach is to reload the view in that method if it is empty, to
make sure that we do not miss that a previously unmounted device has
been re-mounted.

Thanks to Grigoriadis Grigoris for analyzing the root cause of this
issue!

BUG: 161385
FIXED-IN: 4.11.3