private @Nullable NameLocationPair editExtLocation(Object o) {
    NameLocationPair pair = (NameLocationPair)o;
    MapExternalResourceDialog dialog = new MapExternalResourceDialog(pair.getName(), myProject, null, pair.getLocation());
    if (!dialog.showAndGet()) {
      return null;
    }
    setModified(true);
    return new NameLocationPair(dialog.getUri(), dialog.getResourceLocation(), pair.myShared);
  }
private @Nullable NameLocationPair editExtLocation(Object o)