update: add payment app_url alert

app/Http/Controllers/Admin/PaymentController.php

@@ -42,6 +42,9 @@ class PaymentController extends Controller
 
     public function save(Request $request)
     {
+        if (!config('v2board.site.app_url')) {
+            abort(500, '请在站点配置中配置站点地址');
+        }
         if ($request->input('id')) {
             $payment = Payment::find($request->input('id'));
             if (!$payment) abort(500, '支付方式不存在');