qubes-anaconda-addon: don't set default netvm if wasn't created

Fixes QubesOS/qubes-issues#2142

qubes-anaconda-addon/org_qubes_os_initial_setup/gui/spokes/qubes_os.py

@@ -426,7 +426,8 @@ class QubesOsSpoke(FirstbootOnlySpokeMixIn, NormalSpoke):
             self.configure_dom0()
             self.configure_default_template()
             self.configure_qubes()
-            self.configure_network()
+            if self.choice_network.get_selected():
+                self.configure_network()
             if self.choice_usb.get_selected() and not self.choice_usb_with_net.get_selected():
                 # Workaround for #1464 (so qvm.start from salt can't be used)
                 self.run_command(['systemctl', 'start', 'qubes-vm@sys-usb.service'])