network: Fix run-time warning

The "edit" widget is only set as data when there is a connection
(in make_row) so only hide it when there is a connection.

https://bugzilla.gnome.org/show_bug.cgi?id=709555
network: Fix warnings when clicking Wi-Fi network

Those 2 widgets (the edit page, and the spinner) might be available
but we need to read about them from the correct widget, eg. the
GtkListBoxRow, not the GtkBox it contains.

https://bugzilla.gnome.org/show_bug.cgi?id=709555