[Vue] provide 出现 undefined、null 的可能情况

传递 Ref 类型，不要解包传递，即 .value 传递非 Ref 类型，导致后代组件不会更新数据。

file:[Father.vue]
const paper = shallowRef<dia.Paper>();
const graph = shallowRef<dia.Graph>();

// 错误传递
del:[provide("paper", paper.value);
provide("graph", graph.value);]:del

// 正确传递
add:[provide("paper", paper);
provide("graph", graph);]:add

onMounted(() => {
  const jointjs = createJointJs({
    el: "content",
    width: "85vw",
    height: "75vh",
    bgColor: "#ffffff"
  });
});

file:[Child.vue]
const paper = inject("paper");