fix

common/modules/bids/controllers/BidAdminController.php

@@ -115,12 +115,15 @@ class BidAdminController extends AdminController
         $model = BidFile::findOne($id);
         
         if($model) {
+            $path = BidFile::path() . $model->filename;
+            if(file_exists($path)) {
                 return Yii::$app->response->sendFile(BidFile::path() . $model->filename, $model->filename);
-        } else {
-            throw new NotFoundHttpException('The requested page does not exist.');
             }
         }
 
+        throw new NotFoundHttpException('The requested page does not exist.');
+    }
+
     /**
      * Finds the Bid model based on its primary key value.
      * If the model is not found, a 404 HTTP exception will be thrown.