message: fix(Picker): cursor.defaultIndex may be 0
diff: // Utils
  -import { createNamespace, isObject } from '../utils';
  +import { createNamespace, isDef, isObject } from '../utils';
  import { preventDefault } from '../utils/dom/event';
  import { BORDER_UNSET_TOP_BOTTOM } from '../utils/constant';
  import { pickerProps } from './shared';
  @@ -86,7 +86,9 @@ export default createComponent({
  let cursor = { children: this.columns };
  while (cursor && cursor.children) {
  - const defaultIndex = cursor.defaultIndex || +this.defaultIndex;
  + const defaultIndex = isDef(cursor.defaultIndex)
  + ? cursor.defaultIndex
  + : +this.defaultIndex;
  formatted.push({
  values: cursor.children.map((item) => item[this.valueKey]),
  