Cannot approve or pay invoice when related POL has no encumbrance

Overview: User cannot approve or pay invoice when related POL has no Fund distribution/encumbrance. 
Steps to Reproduce:

1. Log into some FOLIO environment as User X
2. Click order app
3. Create PO and POL
4. POL must have price but NO fund distribution
5. Open POL
6. Create invoice
7. Add invoice line for POL created above
8. Approve invoice line

Approach
Skip processing encumbrances if returned collection is empty
org.folio.services.finance.transaction.EncumbranceService#getEncumbrancesByPoLineIds

Expected Results: Invoice is approved successfully. Pending payments are created

Actual Results: Error toast message is shown. Invoice was not approved.

Additional Information: see example at url below
URL: https://thunderjet.ci.folio.org/invoice/view/f673f695-e124-489a-b182-25594fad517a
Interested parties: