message: feat(@vant/use): useParent always return index
diff: import {
  + ref,
  inject,
  computed,
  onUnmounted,
  @@ -18,9 +19,7 @@ export function useParent<T>(key: string | symbol) {
  const parent = inject<ParentProvide<T> | null>(key, null);
  if (parent) {
  - const instance = getCurrentInstance();
  -
  - if (instance) {
  + const instance = getCurrentInstance()!;
  const { link, unlink, internalChildren, ...rest } = parent;
  link(instance);
  @@ -36,7 +35,9 @@ export function useParent<T>(key: string | symbol) {
  index,
  };
  }
  - }
  - return {};
  + return {
  + parent: null,
  + index: ref(-1),
  + };
  }
  