fix segfault
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index fac45fe..9a96a1e 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -2488,7 +2488,9 @@
     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                    "finalize http upstream request: %i", rc);
 
-    *u->cleanup = NULL;
+    if (u->cleanup) {
+        *u->cleanup = NULL;
+    }
 
     if (u->state && u->state->response_sec) {
         tp = ngx_timeofday();