Don't crash trying to render non-existant VAT percentages

The fractional VAT patch did not properly handle the case when the field
could actually be NULL.

1 files changed, 6 insertions, 1 deletions

diff --git a/postgresqleu/util/fields.py b/postgresqleu/util/fields.py
index 8565548a..6e86ceb0 100644
--- a/postgresqleu/util/fields.py
+++ b/postgresqleu/util/fields.py
@@ -122,7 +122,12 @@ class UserModelChoiceField(ModelChoiceField):
 
 class NormalizedDecimalField(models.DecimalField):
     def from_db_value(self, value, expression, connection):
+        if value is None:
+            return value
         return value.quantize(Decimal(1)) if value == value.to_integral() else value.normalize()
 
     def to_python(self, value):
-        return super().to_python(value).quantize(Decimal(1)) if value == value.to_integral() else value.normalize()
+        val = super().to_python(value)
+        if val is None:
+            return val
+        return val.quantize(Decimal(1)) if val == val.to_integral() else val.normalize()