Check ifa->ifa_addr otherwise existing TUN device causes following segfault;

Check ifa->ifa_addr otherwise existing TUN device causes following segfault;

>>> import vserver
>>> q = vserver.VServer("princeton_caglar")
>>> q.set_ipaddresses_config("0.0.0.0")

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1220499776 (LWP 831)]
0xb72a8556 in get_mask (addr=0xbfa7761c) at python/vserverimpl.c:404
404         if (ifa->ifa_addr->sa_family == family &&

tun1095-0 Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)