Don't crash if an invalid always-on VPN profile is configured.

This is currently being hit because Settings does not clear the
always-on VPN configuration when the corresponding VPN profile is
deleted. This will be fixed in Settings, but there's no harm in
being robust to invalid configurations here.

Bug: 23625458
Change-Id: Id185a54d5892339197cd40026df5174debd957cf
1 file changed