Adding a new Payment Instrument does not require account, results in unbalanced transactions

To reproduce this issue:

1) Click "Administer ... CiviContribute ... Payment Instruments"

2) Click "Add Payment Instrument" Fill in anything for the label. do NOT choose anything for "Financial Account"

3) Click "Create New... Contribution" Fill in any amount, any financial type. For "payment instrument" choose the new instrument created in the previous step.

4) Add this contribution to an accounting batch and export the batch. The Debit Columns (Debit Account, Debit Account Name, and Debit Account Type) are empty.