Fixed incompatibility with new version of PyShark or tshark

[krater]

I fixed the [ERROR] Parsing field: ip.addr problem. Looks like tshark or PyShark changed the format a little bit. I tried to make it compatible to both format versions, but can't test it because I have no system where the unpatched polymorph works.

For a little bit more info look at https://github.com/shramos/polymorph/issues/20

Thanks for this really nice tool :D