fix the missing of checking empty queryset; add bills ordering by date

fet2020/finance/admin.py

@@ -103,8 +103,6 @@ class BillPeriodeFilter(admin.SimpleListFilter):
         return self.__lst
 
     def queryset(self, request, queryset):
-        qs = queryset
-
         if self.value():
             try:
                 period = datetime.strptime(self.value()[:4], "%Y")  # noqa: DTZ007
@@ -120,14 +118,15 @@ class BillPeriodeFilter(admin.SimpleListFilter):
 
         # Return bills from current period.
         else:
-            tmp_qs = queryset.order_by("-date")
+            if not queryset.exists():
+                return queryset
 
             # Get first period.
-            start_year = tmp_qs.first().date.year
+            start_year = queryset.first().date.year
 
             # Check if date of first bill is in first half of year. If yes, start of period is the
             # year before.
-            if tmp_qs.first().date < date(start_year, 7, 1):
+            if queryset.first().date < date(start_year, 7, 1):
                 start_year -= 1
 
             start_date = date(start_year, 7, 1)

fet2020/finance/models.py

@@ -217,6 +217,8 @@ class Bill(models.Model):
         verbose_name = "Rechnung"
         verbose_name_plural = "Rechnungen"
 
+        ordering = ["-date"]
+
     def __str__(self):
         return f"{self.purpose}"