question: adapt this converter to call the specified fallback converter when this converter returns null fora non-null input . concode_field_sep PlaceHolder placeHolder concode_field_sep ValueConverter nullOr concode_elem_sep ValueConverter and concode_elem_sep ValueConverter passthrough concode_elem_sep Object convert
target: ValueConverter function ( ValueConverter arg0 ) { if ( arg0 == null ) return this ; return ( data ) -> { Object loc0 = convert ( data ) ; return loc0 != null || data == null ? loc0 : arg0 . convert ( data ) ; } ; }