Fixing invalid message received in nh --get o/p

Skipping sub-nh expansion for composite nh case if the index is -1
in nh utility.

Change-Id: If6ef6424a67f96478d8cb740479728754b0d431f
Closes-Bug: #1670820

utils/nh.c

@@ -372,6 +372,9 @@ vr_nexthop_req_process(void *s_req)
     if (command == SANDESH_OP_GET) {
         if (req->nhr_type == NH_COMPOSITE) {
             for (i = 0; i < req->nhr_nh_list_size; i++) {
+                // Skip expanding sub-nh for -1 index
+                if (req->nhr_nh_list[i] == -1)
+                    continue;
                 vr_nh_op(cl, command, type, req->nhr_nh_list[i], if_id, vrf_id,
                             dst_mac, src_mac, sip, dip, flags);
             }