Context: Delphi 10.2 / Intraweb

Hello

I installed BDD components in UserSessionUnit, then a DataSource in Unit1.an IWButton in Unit1.with the code:
procedure TIWForm1.IWButton1Click (Sender: TObject);beginDataSource1.DataSet.Open;end;
Compilation without problem, but at the execution I get:Error :Violation of access to the address 007801A7 in module 'test.exe'. Reading address 00000000
Do you have an idea ? thank you