function toUserCoordinate(coordinate, sourceProjection) {
  if (!userProjection) {
    return coordinate;
  }
  return transform(coordinate, sourceProjection, userProjection);
}
Return a coordinate transformed into the user projection.  If no user projection
is set, the original coordinate is returned.
@param {Array<number>} coordinate Input coordinate.
@param {ProjectionLike} sourceProjection The input coordinate projection.
@return {Array<number>} The input coordinate in the user projection.