RIOT-OS/RIOT — pull request #1796 by fabianbrandt (2014-10-10 15:21:04+00:00)
Title: Fixes when a packet is not for me, but an interface is defined.

It´s just wrong logic as it is now - likely self-explainable. It should only ignore handling the packet, if no interface is defined, which means, the int variable is less than zero.