Fix invoice duplication when importing payments for expired orders

src/pretix/base/services/invoices.py

@@ -203,7 +203,7 @@ def build_cancellation(invoice: Invoice):
 
 
 def generate_cancellation(invoice: Invoice, trigger_pdf=True):
-    if invoice.refered.exists():
+    if invoice.canceled:
         raise ValueError("Invoice should not be canceled twice.")
     cancellation = modelcopy(invoice)
     cancellation.pk = None

src/pretix/base/services/orders.py

@@ -1753,7 +1753,7 @@ def change_payment_provider(order: Order, payment_provider, amount=None, new_pay
 
     if recreate_invoices:
         i = order.invoices.filter(is_cancellation=False).last()
-        if i and order.total != oldtotal:
+        if i and order.total != oldtotal and not i.canceled:
             generate_cancellation(i)
             generate_invoice(order)