Couldn't convert varient of type (NULL) into type (String)

[Svenkan]

Delphi-Quellcode:

for count := 1 to Pred(Query2.RecordCount) do begin
  Query2.FieldValues['WER'].isNull;
  Query2.FieldValues['FUER'].isNull;
  Query2.FieldValues['RAUM'].isNull;
  Query2.FieldValues['BEMER_SCH'].isNull;