examples/ipsec-secgw: fix inbound SA checking
examples/ipsec-secgw: fix inbound SA checking

In the inbound_sa_check() make sure that sa pointer stored
inside mbuf private area is not NULL.

Fixes: d299106e8e31 ("examples/ipsec-secgw: add IPsec sample application")
Cc: stable@dpdk.org

Signed-off-by: Bernard Iremonger <233eeff376ad0c06f66f06c5522ea3c4feb30d3b@intel.com>
Acked-by: Radu Nicolau <fa459cf59d47c122ba776e9a6f631c862bf44680@intel.com>
Acked-by: Akhil Goyal <74d7c4c993a22c1d4f60c46ff3d95c969a24a25c@nxp.com>
Signed-off-by: Konstantin Ananyev <cbd5212b59ab42a210d72992d23a3aa17cfd3eaf@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk