Bugfix: when adding data indexes are filled with "undefined"

When adding data then data in the columns (that represent indexes) was always "undefined" - the reason was that the string "data" wasn't converted to an object before accessing the members.

<b>This fix only fixes <i>inserting</i> of data, updating of the Indexed object member will not be reflected in the data being changed in the column; that's another one to look at!</b>