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

@@ -117,9 +117,9 @@ class EmInvoice extends Base
         $eiu = EmInvoiceUseage::where(['invoice_id'=>$inv->invoice_id])->find();
 
         //查询抄表信息
-        $useage = Useage::with('photo')->get(['useage_id'=>$eiu->useage_id]);
 
-        if(is_int($useage->photo_id) && $useage->photo_id != 0) {
+        $useage = Useage::with('photo')->get(['useage_id'=>$eiu->useage_id]);
+        if(isset($useage->photo_id) && is_int($useage->photo_id) && $useage->photo_id != 0) {
             $receipt = Receipt::get(['id'=>$useage->photo_id ?: 0]);
             if($receipt) $useage['photo'] = $receipt;
         } else {