Fixed bug in Sniffer::next_packet.
Fixed bug in Sniffer::next_packet.

hanw/libtins,viveks9/decrypt80211,UlfWetzker/libtins,rklabs/libtins,capturePointer/libtins,capturePointer/libtins,mfontanini/libtins,viveks9/decrypt80211,wavelets/libtins,wavelets/libtins,zmb3/libtins,UlfWetzker/libtins,bowlofstew/libtins,bowlofstew/libtins,hanw/libtins,mfontanini/libtins,salessandri/libtins,zmb3/libtins,salessandri/libtins,rklabs/libtins