fix return value on failure

src/http/ngx_http_script.c

diff --git a/src/http/ngx_http_script.c b/src/http/ngx_http_script.c
index b8e998a..dbe6c34 100644
--- a/src/http/ngx_http_script.c
+++ b/src/http/ngx_http_script.c
@@ -561,7 +561,7 @@
 
     new = ngx_array_push_n(codes, size);
     if (new == NULL) {
-        return NGX_CONF_ERROR;
+        return NULL;
     }
 
     if (code) {