diff --git a/lib/assigner.rb b/lib/assigner.rb
index cbbb977..8e37978 100644
--- a/lib/assigner.rb
+++ b/lib/assigner.rb
@@ -461,10 +461,13 @@ class ::Assigner
 
   def invite_group(group)
     return if topic.topic_allowed_groups.exists?(group_id: group.id)
-    return if topic.all_allowed_users
-                .joins("RIGHT JOIN group_users ON group_users.user_id = users.id")
-                .where("group_users.group_id = ? AND users.id IS NULL", group.id)
-                .empty? # all group members can already see the topic
+    if topic
+         .all_allowed_users
+         .joins("RIGHT JOIN group_users ON group_users.user_id = users.id")
+         .where("group_users.group_id = ? AND users.id IS NULL", group.id)
+         .empty?
+      return # all group members can already see the topic
+    end
 
     guardian.ensure_can_invite_group_to_private_message!(group, topic)
     topic.invite_group(@assigned_by, group)
diff --git a/spec/lib/assigner_spec.rb b/spec/lib/assigner_spec.rb
index 965de7e..534ca1f 100644
--- a/spec/lib/assigner_spec.rb
+++ b/spec/lib/assigner_spec.rb
@@ -747,13 +747,14 @@ RSpec.describe Assigner do
 
     it "doesn't invite group if all members have access to the PM already" do
       user1, user2, user3 = 3.times.collect { Fabricate(:user) }
-      group1, group2, group3 = 3.times.collect do
-        Fabricate(
-          :group,
-          assignable_level: Group::ALIAS_LEVELS[:only_admins],
-          messageable_level: Group::ALIAS_LEVELS[:only_admins],
-        )
-      end
+      group1, group2, group3 =
+        3.times.collect do
+          Fabricate(
+            :group,
+            assignable_level: Group::ALIAS_LEVELS[:only_admins],
+            messageable_level: Group::ALIAS_LEVELS[:only_admins],
+          )
+        end
       group1.add(user1)
       group1.add(user3)
       group2.add(user2)