Nil check ingressSandbox before deleting
Nil check ingressSandbox before deleting

Signed-off-by: Jana Radhakrishnan <045898bda7d4800fe4909a9831e702ab79e266be@docker.com>

medallia/libnetwork,abhi/libnetwork,docker/libnetwork,WeiZhang555/libnetwork,mYmNeo/libnetwork,msabansal/libnetwork,WeiZhang555/libnetwork,tmakita/libnetwork,mahak/libnetwork,mYmNeo/libnetwork,mbanikazemi/libnetwork,allencloud/libnetwork,mbanikazemi/libnetwork,docker/libnetwork,kolyshkin/libnetwork,allencloud/libnetwork,medallia/libnetwork,medallia/libnetwork,vdemeester/libnetwork,abhi/libnetwork,ityangchen/libnetwork,curtiszimmerman/libnetwork,abhi/libnetwork,ityangchen/libnetwork,mahak/libnetwork,mahak/libnetwork,vdemeester/libnetwork,docker/libnetwork,sainath14/libnetwork,vdemeester/libnetwork,tmakita/libnetwork,sainath14/libnetwork,fcrisciani/libnetwork,msabansal/libnetwork,kolyshkin/libnetwork,cpuguy83/libnetwork,curtiszimmerman/libnetwork,cpuguy83/libnetwork,kolyshkin/libnetwork,fcrisciani/libnetwork