Exclude vouchers with empty accountingCode from batchVoucher generation

Overview:
Since the accountingCode field become optional in voucher schema and still required in batchedVoucher schema. Error will occurs upon batchVoucher generation if voucher accountingCode field is empty.

Steps to Reproduce:
Create invoice
Use vendor with no accounting code information
DO NOT toggle "Export to accounting"
create invoice line
Approve invoice
Run manual batch voucher export

Expected Results:
Batch voucher generated successfully. Voucher without accountingCode not added to batchVoucher - TBC dennisbridges If possible, this should be based on whether "Export to accounting" is true or not, rather than the presence of the accounting code. That said, this would work as a 'fix' for the release.

Actual Results:
Error occurs upon batchVoucher generation