Fix: don't show tva with rate 0

htdocs/includes/modules/commande/pdf_einstein.modules.php

htdocs/includes/modules/facture/doc/pdf_crabe.modules.php

htdocs/includes/modules/facture/doc/pdf_oursin.modules.php

htdocs/includes/modules/propale/pdf_propale_azur.modules.php

...udes/modules/supplier_invoice/pdf/pdf_canelle.modules.php

...ludes/modules/supplier_order/pdf/pdf_muscadet.modules.php

htdocs/lib/pdf.lib.php