LISP: fix crash when adding a negative forwarding entry, VPP-681
LISP: fix crash when adding a negative forwarding entry, VPP-681

Change-Id: I190696da5555c05074ee0eee32eb914bd16e38fb
Signed-off-by: Filip Tehlar <9891019d6f5d48a43af8fb71dfec78974db6001d@cisco.com>

chrisy/vpp,vpp-dev/vpp,chrisy/vpp,vpp-dev/vpp,FDio/vpp,milanlenco/vpp,vpp-dev/vpp,vpp-dev/vpp,milanlenco/vpp,FDio/vpp,milanlenco/vpp,milanlenco/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,vpp-dev/vpp,milanlenco/vpp,milanlenco/vpp,chrisy/vpp,vpp-dev/vpp,FDio/vpp,vpp-dev/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp