解决弹出的打印界面存在缓存的bug

jshERP-web/src/views/bill/dialog/BillPrintIframe.vue

@@ -59,6 +59,7 @@
         this.close()
       },
       close() {
+        this.billPrintUrl = ''
         this.$emit('close');
         this.visible = false;
       }