gnrc_ipv6: allow sending empty IPv6 packets
gnrc_ipv6: allow sending empty IPv6 packets

authmillenon/RIOT,jasonatran/RIOT,cladmi/RIOT,mfrey/RIOT,OTAkeys/RIOT,yogo1212/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,miri64/RIOT,toonst/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,jasonatran/RIOT,ant9000/RIOT,lazytech-org/RIOT,kYc0o/RIOT,aeneby/RIOT,OlegHahm/RIOT,OlegHahm/RIOT,ant9000/RIOT,basilfx/RIOT,josephnoir/RIOT,jasonatran/RIOT,toonst/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,mfrey/RIOT,cladmi/RIOT,mfrey/RIOT,josephnoir/RIOT,mfrey/RIOT,rfuentess/RIOT,OTAkeys/RIOT,kYc0o/RIOT,josephnoir/RIOT,smlng/RIOT,miri64/RIOT,rfuentess/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,basilfx/RIOT,josephnoir/RIOT,yogo1212/RIOT,mtausig/RIOT,smlng/RIOT,x3ro/RIOT,mtausig/RIOT,kYc0o/RIOT,x3ro/RIOT,mtausig/RIOT,smlng/RIOT,OlegHahm/RIOT,toonst/RIOT,aeneby/RIOT,aeneby/RIOT,mtausig/RIOT,x3ro/RIOT,yogo1212/RIOT,basilfx/RIOT,miri64/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kaspar030/RIOT,ant9000/RIOT,aeneby/RIOT,authmillenon/RIOT,ant9000/RIOT,kaspar030/RIOT,lazytech-org/RIOT,smlng/RIOT,cladmi/RIOT,jasonatran/RIOT,smlng/RIOT,lazytech-org/RIOT,miri64/RIOT,toonst/RIOT,miri64/RIOT,kYc0o/RIOT,x3ro/RIOT,OlegHahm/RIOT,rfuentess/RIOT,rfuentess/RIOT,rfuentess/RIOT,yogo1212/RIOT,josephnoir/RIOT,yogo1212/RIOT,aeneby/RIOT,mfrey/RIOT,RIOT-OS/RIOT,lazytech-org/RIOT,lazytech-org/RIOT,cladmi/RIOT,toonst/RIOT,authmillenon/RIOT,ant9000/RIOT,kaspar030/RIOT,authmillenon/RIOT,basilfx/RIOT,yogo1212/RIOT,authmillenon/RIOT,jasonatran/RIOT,mtausig/RIOT,cladmi/RIOT,RIOT-OS/RIOT,x3ro/RIOT,basilfx/RIOT