修复缴费单显示错误

application/em/view/payment/detail.html

@@ -121,7 +121,7 @@
                                             <td>{$item.em_numb}</td>
                                             <td>{$item.payment_amount}</td>
                                             <td><input name="paid[{$item.invoice_id}][paid_amount]" type="text" 
-                                                   class="layui-input no-border paid_amount" value="{$item.payment_amount - $item.payment_balance}" disabled="disabled"></td>
+                                                   class="layui-input no-border paid_amount" value="{if isset($item.payment_amount)}{$item.payment_amount - $item.payment_balance}{else /} {/if}" disabled="disabled"></td>
                                         </tr>
                                         {/volist}
                                         </tbody>