[damned-lies] Avoid null values in total_for_lang method

[Claude Paroz <claudep src gnome org>]

commit f0d5dec264a74a79e8ce93676e77978b9003e318
Author: Claude Paroz <claude 2xlibre net>
Date:   Sun Mar 21 15:26:57 2021 +0100

    Avoid null values in total_for_lang method

 stats/models.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/stats/models.py b/stats/models.py
index bdcde8c1..29eb845f 100644
--- a/stats/models.py
+++ b/stats/models.py
@@ -1052,8 +1052,12 @@ class Release(models.Model):
         query = Statistics.objects.filter(language=lang, branch__releases=self
             ).exclude(domain__in=self.excluded_domains
             ).values('domain__dtype'
-            ).annotate(trans=models.Sum('full_po__translated'), fuzzy=models.Sum('full_po__fuzzy'),
-                       trans_p=models.Sum('part_po__translated'), fuzzy_p=models.Sum('part_po__fuzzy'))
+            ).annotate(
+                trans=Coalesce(models.Sum('full_po__translated'), models.Value(0)),
+                fuzzy=Coalesce(models.Sum('full_po__fuzzy'), models.Value(0)),
+                trans_p=Coalesce(models.Sum('part_po__translated'), models.Value(0)),
+                fuzzy_p=Coalesce(models.Sum('part_po__fuzzy'), models.Value(0))
+            )
         stats = {'id': self.id, 'name': self.name, 'description': _(self.description),
                  'ui':  {'translated': 0, 'fuzzy': 0, 'total': total_ui,
                          'translated_perc': 0, 'fuzzy_perc': 0, 'untranslated_perc': 0,