[FIX] account_asset: asset_create

When creating assets from invoice lines, the system must check
that assets have not already been created for the related invoice.
If assets already exist then these assets have to be removed.

Used case:

- In the purchase journal, tick "allow canceling entries"
- On a supplier invoice line, set an asset category
- validate the invoice
- cancel the invoice
- set to draft
- validate the invoice

Before the fix: the asset is created twice.
After the fix: the asset is created once.

opw:674674