This fixes the "REAL"->"TEXT" issue.
There was an issue (Thanks, @tsulaia for spotting that!) causing a table to store auxiliary data being created with TEXT column type instead of REAL under specific circumstances.
Basically, the affected columns have empty entries in the first rows. Those empty entries were correctly filled with 'null'. But 'null' was taken as text type by the std::holds_alternative<...>() check, and the column got created as 'TEXT'.
This MR is related to and is needed by https://gitlab.cern.ch/atlas/geomodelatlas/GeoModelATLAS/-/merge_requests/8