GUACAMOLE-514: use correct client in log call.
diff --git a/src/protocols/vnc/auth.c b/src/protocols/vnc/auth.c
index 0c39e94..e03be53 100644
--- a/src/protocols/vnc/auth.c
+++ b/src/protocols/vnc/auth.c
@@ -55,8 +55,7 @@
         return creds;
     }
     
-    guac_client_log(client, GUAC_LOG_ERROR,
-            "Unknown credential type requested.");
+    guac_client_log(gc, GUAC_LOG_ERROR, "Unknown credential type requested.");
     return NULL;
     
 }