message: handle nullish values in SelectControl
diff: @@ -349,7 +349,7 @@ export class SelectControl extends React.PureComponent<ParamProps<PD.Select<stri
  renderControl() {
  const items = this.items(this.props.param);
  - const current = this.props.value ? ActionMenu.findCurrent(items, this.props.value) : void 0;
  + const current = this.props.value !== undefined ? ActionMenu.findCurrent(items, this.props.value) : void 0;
  const label = current
  ? current.label
  : typeof this.props.value === 'undefined'
  