Approval allowed for 0 amount invoice and invoices with 0 amount invoice lines

Overview: If a user creates an invoice with a $0.00 cost because all invoice lines are for 0 dollars, they are able to approve the invoice, but unable to pay the invoice. The payment attempt results in an error.
Steps to Reproduce:

1. Log into https://folio-iris.dev.folio.org/ as a user with admin permissions.
2. Create an order with a $0.00 cost and fund distribution.
3. Create an invoice and add the order from step 2 as an invoice line.
4. Approve the invoice.

Expected Results: Approval fails due to a restriction on approving $0.00 invoices.

Actual Results: Approval is successful, but payment attempts receive the following error: 
One or more transactions record(s) failed to be created

Additional Information: 
The network response is:

 {
 "errors" : [ {
 "message" : "One or more transactions record(s) failed to be created",
 "code" : "transactionCreationFailure",
 "parameters" : [
{ "key" : "invoiceLineId", "value" : "c44f16b5-1b91-4dbc-8fe8-ce2d3b016ccd" },

{ "key" : "fundId" }
]
 } ],
 "total_records" : 1
 }

 
Normally, this scenario would not occur as the preferred workflow would be to make the payment status on the order 'Payment not required' and avoid invoicing altogether. However, this bug is meant to address the erroneous successful approval action.

Interested parties: mdriscoll ama8crow@gmail.com