Resolve "Allow more than one person without e-mail address to be invited"

Closes #652 (closed)

aleksis/core/views.py

@@ -1447,7 +1447,7 @@ class InvitePersonByID(PermissionRequiredMixin, SingleObjectMixin, View):
     def get(self, request, *args, **kwargs):
         person = self.get_object()
 
-        if not PersonInvitation.objects.filter(email=person.email).exists():
+        if not person.email or not PersonInvitation.objects.filter(email=person.email).exists():
             length = get_site_preferences()["auth__invite_code_length"]
             packet_size = get_site_preferences()["auth__invite_code_packet_size"]
             key = generate_random_code(length, packet_size)