修复账单如果没有附件则现实错误页面的问题

application/em/model/EmInvoice.php

@@ -120,7 +120,7 @@ class EmInvoice extends Base
         $useage = Useage::with('photo')->get(['useage_id'=>$eiu->useage_id]);
 
         if(is_int($useage->photo_id) && $useage->photo_id != 0) {
-            $receipt = Receipt::get(['id'=>$useage->photo_id]);
+            $receipt = Receipt::get(['id'=>$useage->photo_id ?: 0]);
             if($receipt) $useage['photo'] = $receipt;
         } else {
             $useage['photo'] = [];