Fixed request finalization in ngx_http_index_handler().

Returning 500 instead of NGX_ERROR is preferable here because
header has not yet been sent to the client.

src/http/modules/ngx_http_index_module.c

diff --git a/src/http/modules/ngx_http_index_module.c b/src/http/modules/ngx_http_index_module.c
index c144b31..2ee1dd5 100644
--- a/src/http/modules/ngx_http_index_module.c
+++ b/src/http/modules/ngx_http_index_module.c
@@ -163,7 +163,7 @@
 
             name = ngx_http_map_uri_to_path(r, &path, &root, reserve);
             if (name == NULL) {
-                return NGX_ERROR;
+                return NGX_HTTP_INTERNAL_SERVER_ERROR;
             }
 
             allocated = path.data + path.len - name;