Improvement process numbers purchase invoices

If purchase invoices were created in multiple session simultaneously, it could happen that the following message appeared when saving: "Process number 'xxxxxxxx' for purchase invoice already exists as prepayment. Please make the ranges unique in the administration settings."
This occurred when the user wanted to save a purchase invoice, whose Purchase Invoice number was already in use.

From now on, the purchase invoice number will be automatically incremented when saving, if the number is already in use.
Previously, this already happened when working via the Purchase Invoice List, now also when creating manual purchase invoices and process purchase invoices where the rules are not applied via the Purchase List.

Note:

• Automatically raising the purchase invoice number does not happen if a different purchase invoice number has been manually entered. (Number does not start with the predecessor as set up in the administration settings)
• In that case, the following message appears: "Purchase invoice 'xxxxxxxx' already exists in the system. | 184"