FIX: error anonymous when tl4_delete_posts_and_topics setting (#20257)

Bug introduced in this PR: https://github.com/discourse/discourse/pull/19946

When the setting is enabled, an error is triggered for anonymous users.

lib/guardian/topic_guardian.rb

@@ -143,7 +143,7 @@ module TopicGuardian
 
   def can_recover_topic?(topic)
     if is_staff? || (topic&.category && is_category_group_moderator?(topic.category)) ||
-         (SiteSetting.tl4_delete_posts_and_topics && user.has_trust_level?(TrustLevel[4]))
+         (SiteSetting.tl4_delete_posts_and_topics && user&.has_trust_level?(TrustLevel[4]))
       !!(topic && topic.deleted_at)
     else
       topic && can_recover_post?(topic.ordered_posts.first)
@@ -212,7 +212,7 @@ module TopicGuardian
 
   def can_see_deleted_topics?(category)
     is_staff? || is_category_group_moderator?(category) ||
-      (SiteSetting.tl4_delete_posts_and_topics && user.has_trust_level?(TrustLevel[4]))
+      (SiteSetting.tl4_delete_posts_and_topics && user&.has_trust_level?(TrustLevel[4]))
   end
 
   # Accepts an array of `Topic#id` and returns an array of `Topic#id` which the user can see.

spec/lib/guardian/topic_guardian_spec.rb

@@ -94,6 +94,38 @@ RSpec.describe TopicGuardian do
       SiteSetting.tl4_delete_posts_and_topics = true
       expect(Guardian.new(tl4_user).can_see_deleted_topics?(topic.category)).to eq(true)
     end
+
+    it "returns false for anonymous user" do
+      SiteSetting.tl4_delete_posts_and_topics = true
+      expect(Guardian.new.can_see_deleted_topics?(topic.category)).to be_falsey
+    end
+  end
+
+  describe "#can_recover_topic?" do
+    fab!(:deleted_topic) { Fabricate(:topic, category: category, deleted_at: 1.day.ago) }
+    it "returns true for staff" do
+      expect(Guardian.new(admin).can_recover_topic?(Topic.with_deleted.last)).to eq(true)
+    end
+
+    it "returns true for group moderator" do
+      SiteSetting.enable_category_group_moderation = true
+      expect(Guardian.new(user).can_recover_topic?(Topic.with_deleted.last)).to eq(false)
+      category.update!(reviewable_by_group_id: group.id)
+      group.add(user)
+      topic.update!(category: category)
+      expect(Guardian.new(user).can_recover_topic?(Topic.with_deleted.last)).to eq(true)
+    end
+
+    it "returns true when tl4 can delete posts and topics" do
+      expect(Guardian.new(tl4_user).can_recover_topic?(Topic.with_deleted.last)).to eq(false)
+      SiteSetting.tl4_delete_posts_and_topics = true
+      expect(Guardian.new(tl4_user).can_recover_topic?(Topic.with_deleted.last)).to eq(true)
+    end
+
+    it "returns false for anonymous user" do
+      SiteSetting.tl4_delete_posts_and_topics = true
+      expect(Guardian.new.can_recover_topic?(Topic.with_deleted.last)).to eq(false)
+    end
   end
 
   describe "#can_edit_topic?" do