ip6_to_ip4.h coverity fix

Change-Id: Ia11fa42d1f2b21a6195e7dc890f958830f83d3a7
Signed-off-by: Matus Fabian <matfabia@cisco.com>
diff --git a/src/vnet/ip/ip6_to_ip4.h b/src/vnet/ip/ip6_to_ip4.h
index f5d5688..92f73ba 100644
--- a/src/vnet/ip/ip6_to_ip4.h
+++ b/src/vnet/ip/ip6_to_ip4.h
@@ -479,7 +479,7 @@
 {
   ip6_header_t *ip6;
   u16 *checksum;
-  ip_csum_t csum;
+  ip_csum_t csum = 0;
   ip4_header_t *ip4;
   u16 fragment_id;
   u16 flags;