Index: /trunk/src/VBox/Devices/Network/slirp/dnsproxy/dnsproxy.c
===================================================================
--- /trunk/src/VBox/Devices/Network/slirp/dnsproxy/dnsproxy.c	(revision 50672)
+++ /trunk/src/VBox/Devices/Network/slirp/dnsproxy/dnsproxy.c	(revision 50673)
@@ -121,7 +121,6 @@
     AssertPtrReturnVoid(arg);
 
-    de = TAILQ_PREV(req->dns_server, dns_list_head, de_list);
-
-    if (de == NULL)
+    if (   req->dns_server == NULL
+        || (de = TAILQ_PREV(req->dns_server, dns_list_head, de_list)) == NULL)
     {
         hash_remove_request(pData, req);