private @Nullable NameLocationPair addExtLocation() {
    MapExternalResourceDialog dialog = new MapExternalResourceDialog(null, myProject, null, null);
    if (!dialog.showAndGet()) {
      return null;
    }
    setModified(true);
    return new NameLocationPair(dialog.getUri(), dialog.getResourceLocation(), false);
  }
private @Nullable NameLocationPair addExtLocation()