debug-validation: fix packet check

On fragments and invalid packets we can have p->proto set, while the
matching protocol header pointer is null.

src/util-validate.h

@@ -73,6 +73,7 @@
         if ((p)->flow != NULL) {                    \
             DEBUG_VALIDATE_FLOW((p)->flow);         \
         }                                           \
+        if (!((p)->flags & (PKT_IS_FRAGMENT|PKT_IS_INVALID))) {          \
             if ((p)->proto == IPPROTO_TCP) {            \
                 BUG_ON((p)->tcph == NULL);              \
             } else if ((p)->proto == IPPROTO_UDP) {     \
@@ -84,6 +85,7 @@
             } else if ((p)->proto == IPPROTO_ICMPV6) {  \
                 BUG_ON((p)->icmpv6h == NULL);           \
             }                                           \
+        }                                           \
         if ((p)->payload_len > 0) {                 \
             BUG_ON((p)->payload == NULL);           \
         }                                           \