Although it is not possible to tell for sure without looking at your form, the place where you have the TDatasource defined suggests that you have not dropped a TDataSource on the form, but coded it yourself.
If so, then I do not see the TDatasource variable ds being created anywhere, which would explain the SIGSEGV.
Either code a create of "ds" or drop a TDataSource onto your form (or better, use a DataModule to separate view and model code).