Fix snapshot updating issues

nummi/main/views.py

@@ -142,7 +142,10 @@ def snapshot(request, date=None):
 
 @login_required
 def update_snapshot(request, uuid):
-    _snapshot, _ = Snapshot.objects.get_or_create(id=uuid)
+    try:
+        _snapshot = Snapshot.objects.get(id=uuid)
+    except Snapshot.DoesNotExist:
+        _snapshot = Snapshot(id=uuid)
     _form = SnapshotForm(request.POST, instance=_snapshot)
     _form.save()
     return redirect(snapshot, date=_snapshot.date)