修改vue-ant-design框架中的form表单校验在ie浏览器中打开后默认校验，输入框出现错误提示的bug

<a-form-item >

                          <a-input

                            placeholder="用户名"

                              v-decorator="[

                                'userName',

                                {rules: [{ required: true, message: '请填写用户名' }], validateTrigger:'blur'}//设置此属性设置当输入框失焦时去校验

                              ]"

                            />

                      </a-form-item>