Joined properties not sortable is RowRenderer

[molshoop]

If I join properties via the @MetaDisplayProperty (see below), I can't make this column sortable via the property defaultSortColumn.

  @MetaDisplayProperty(name = "standardStreetName", displayLength = 20, join = " ")
, @MetaDisplayProperty(name = "houseNumber", displayLength = 10, join = "")
, @MetaDisplayProperty(name = "houseLetters")