basic: remove use of sal_uIntptr in favor of more appropriate type

Change-Id: Ie878f43c7245838519fe7477b039827b079dde63
Reviewed-on: https://gerrit.libreoffice.org/8214
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>