bugfix: improve htAmount calculation

djangoldp_invoice/models.py

@@ -61,11 +61,11 @@ class CustomerInvoice(Model):
     additionalText = models.CharField(max_length=255, blank=True, null=True)
 
     def htAmount(self):
-        htAmount = Decimal(0)
-        if self.batches is None:
-            htAmount = self.batches.aggregate(total=Sum('tasks__htAmount'))['total']
+        amount = Task.objects.filter(batch__invoice = self).aggregate(total=Sum('htAmount'))['total']
+        if amount is None:
+            amount = Decimal(0.0)
+        return amount
 
-        return htAmount
 
     def tvaAmount(self):
         return Decimal(self.tvaRate * self.htAmount() / Decimal(100))