[master] dfc31fda4 Null check

[Dridi Boukelmoune]

commit dfc31fda49ff0bcf49d6602d9c0040bc3377073b
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Wed Feb 6 18:39:33 2019 +0100

    Null check
    
    Apologies for the spam, I didn't think this would be a recurring
    pattern.

diff --git a/bin/varnishd/cache/cache_esi_deliver.c b/bin/varnishd/cache/cache_esi_deliver.c
index 59a138bb2..eeb4d1e79 100644
--- a/bin/varnishd/cache/cache_esi_deliver.c
+++ b/bin/varnishd/cache/cache_esi_deliver.c
@@ -301,6 +301,7 @@ ved_vdp_esi_bytes(struct req *req, enum vdp_action act, void **priv,
 	struct ecx *ecx;
 	int retval = 0;
 
+	AN(priv);
 	CAST_OBJ_NOTNULL(ecx, *priv, ECX_MAGIC);
 	pp = ptr;