Only release VCL if we have one

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5481 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_pool.c

@@ -190,8 +190,10 @@ wrk_thread_real(struct wq *qp, unsigned shm_workspace, unsigned sess_workspace,
 		AZ(w->wfd);
 		assert(w->wlp == w->wlb);
 		w->wrq = NULL;
-		if (params->diag_bitmap & 0x00040000)
-			VCL_Rel(&w->vcl);
+		if (params->diag_bitmap & 0x00040000) {
+			if (w->vcl != NULL)
+				VCL_Rel(&w->vcl);
+		}
 		if (!Lck_Trylock(&wstat_mtx)) {
 			wrk_sumstat(w);
 			Lck_Unlock(&wstat_mtx);

bin/varnishd/cache_vcl.c

@@ -104,6 +104,7 @@ VCL_Rel(struct VCL_conf **vcc)
 {
 	struct VCL_conf *vc;
 
+	AN(*vcc);
 	vc = *vcc;
 	*vcc = NULL;