skip validating errors is session isn't loaded (#380)

Author: timrspratt

src/Middleware.php

@@ -145,7 +145,7 @@ public function onVersionChange(Request $request, Response $response): Response
      */
     public function resolveValidationErrors(Request $request)
     {
-        if (! $request->session()->has('errors')) {
+        if (! $request->hasSession() || ! $request->session()->has('errors')) {
             return (object) [];
         }