use vue-sortable to report an error in vue2.0, and the error message is as follows:
[Vue warn]: Error in directive sortable update hook: "Sortable: el must be HTMLElement, and not [object Undefined]"
the code for using sortable is as follows:

import Sortable from "vue-sortable"
Vue.use(Sortable);

        <div id="frame_layout"  v-sortable>

            <div class="frame_group_div">
                1
            </div>

            <div class="frame_group_div">
                2
            </div>
            <div class="frame_group_div">
                3
            </div>
        </div>

github. How to use vue-sortable? in vue?