Properly reset paid date through WC_Order->set_date_paid(null)

[ole1986]

Should be

$order->set_date_paid( null ); // Löscht den Zeitstempel im Objekt
$order->save();                // Schreibt 'null' zurück in die DB

wc-invoice-pdf/src/WcExtend/InvoiceMetabox.php

Lines 45 to 46 in ff78045

	delete_post_meta($order_id, '_date_paid');
	delete_post_meta($order_id, '_paid_date');