[master] dea77acca avoid null pointer deref in panic code

[Nils Goroll]

commit dea77acca891aff4f46fc60f61f37d018e3c22a2
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Sun Jul 21 13:03:38 2019 +0200

    avoid null pointer deref in panic code

diff --git a/bin/varnishd/cache/cache_panic.c b/bin/varnishd/cache/cache_panic.c
index 60a521ece..8a9c88775 100644
--- a/bin/varnishd/cache/cache_panic.c
+++ b/bin/varnishd/cache/cache_panic.c
@@ -533,7 +533,7 @@ pan_req(struct vsb *vsb, const struct req *req)
 	if (VALID_OBJ(req->htc, HTTP_CONN_MAGIC))
 		pan_htc(vsb, req->htc);
 	pan_http(vsb, "req", req->http);
-	if (req->resp->ws != NULL)
+	if (req->resp != NULL && req->resp->ws != NULL)
 		pan_http(vsb, "resp", req->resp);
 	if (req->vdc != NULL)
 		pan_vdp(vsb, req->vdc);