Resolve "Group query fails in some cases (probably when queried by a member/owner)"

Closes #895 (closed)

One can only combine two querysets using |, not a queryset and e.g. a Person.

aleksis/core/schema/group.py

@@ -39,7 +39,7 @@ class GroupType(DjangoObjectType):
         if has_person(info.context.user) and [
             m for m in root.members.all() if m.pk == info.context.user.person.pk
         ]:
-            persons = (persons | Person.objects.get(pk=info.context.user.person.pk)).distinct()
+            persons = (persons | Person.objects.filter(pk=info.context.user.person.pk)).distinct()
         return persons
 
     @staticmethod
@@ -48,7 +48,7 @@ class GroupType(DjangoObjectType):
         if has_person(info.context.user) and [
             o for o in root.owners.all() if o.pk == info.context.user.person.pk
         ]:
-            persons = (persons | Person.objects.get(pk=info.context.user.person.pk)).distinct()
+            persons = (persons | Person.objects.filter(pk=info.context.user.person.pk)).distinct()
         return persons
 
     @staticmethod