@NotNull
  private static SdkListItem unwrapItem(@Nullable JdkComboBoxItem item) {
    if (item == null) item = new ProjectJdkComboBoxItem();

    if (item instanceof InnerComboBoxItem) {
      return ((InnerComboBoxItem)item).getItem();
    }
    throw new RuntimeException("Failed to unwrap " + item.getClass().getName() + ": " + item);
  }
@NotNull
  private static SdkListItem unwrapItem(@Nullable JdkComboBoxItem item)