When all firewall rules are removed, qubes-vm-settings crashed
trying to check if the last rule accepts or drops all packages.
It is now verifies that there is a last rule.
Also, it is now properly verified that the last rule accept
or drops all packages.
Associated stack trace:
----
line: last_rule = reversed_rules.pop(0)
func: get_firewall_conf
line no.: 227
file: /usr/lib/python3.5/site-packages/qubesmanager/firewall.py
----
line: conf = self.get_firewall_conf(vm)
func: set_vm
line no.: 308
file: /usr/lib/python3.5/site-packages/qubesmanager/firewall.py
----
line: model.set_vm(vm)
func: __init__
line no.: 111
file: /usr/lib/python3.5/site-packages/qubesmanager/settings.py
----
line: settings_window = VMSettingsWindow(vm, qapp, args.tab)
func: main
line no.: 1133
file: /usr/lib/python3.5/site-packages/qubesmanager/settings.py
----
line: load_entry_point('qubesmanager==4.0.17', 'console_scripts', 'qubes-vm-settings')()
func: <module>
line no.: 9
file: /usr/bin/qubes-vm-settings
031ad02ff6