message: fix(tabs): only deselect on valid new tab
diff: @@ -16,11 +16,11 @@ export class DocsTabs {
  }
  select(tab: HTMLDocsTabElement) {
  + if (tab != null) {
  if (this.selected != null) {
  this.selected.removeAttribute('selected');
  }
  - if (tab != null) {
  this.selected = tab;
  this.selected.setAttribute('selected', '');
  }
  