fib: format deleted LB

This patch allows the formatting of deleted Load-balancer
objects. This is needed in the case a trace references a DPO
that went away in the interim.

Type: improvement

Change-Id: I6d67519b8d62f69aafde3c8fe3065bc85a7adbde
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>
diff --git a/src/vnet/dpo/load_balance.c b/src/vnet/dpo/load_balance.c
index fae7c1d..8f2a0de 100644
--- a/src/vnet/dpo/load_balance.c
+++ b/src/vnet/dpo/load_balance.c
@@ -149,7 +149,13 @@
     dpo_id_t *buckets;
     u32 i;
 
-    lb = load_balance_get(lbi);
+    lb = load_balance_get_or_null(lbi);
+    if (lb == NULL)
+      {
+	s = format(s, "DELETED lb:%u", lbi);
+	return (s);
+      }
+
     vlib_get_combined_counter(&(load_balance_main.lbm_to_counters), lbi, &to);
     vlib_get_combined_counter(&(load_balance_main.lbm_via_counters), lbi, &via);
     buckets = load_balance_get_buckets(lb);