FIX: error when CategoryList tried to find relevant topics (#22339)

Recently, we added the option for watched tag/categories to take precedence over muted tag/categories. Therefore, `remove_muted_tags` is using `category_users` to check if categories are not watched. There was missing join in CategoryList which was causing an error.

app/models/category_list.rb

@@ -86,12 +86,17 @@ class CategoryList
 
     if @guardian.authenticated?
       @all_topics =
-        @all_topics.joins(
-          "LEFT JOIN topic_users tu ON topics.id = tu.topic_id AND tu.user_id = #{@guardian.user.id.to_i}",
-        ).where(
-          "COALESCE(tu.notification_level,1) > :muted",
-          muted: TopicUser.notification_levels[:muted],
-        )
+        @all_topics
+          .joins(
+            "LEFT JOIN topic_users tu ON topics.id = tu.topic_id AND tu.user_id = #{@guardian.user.id.to_i}",
+          )
+          .joins(
+            "LEFT JOIN category_users ON category_users.category_id = topics.category_id AND category_users.user_id = #{@guardian.user.id}",
+          )
+          .where(
+            "COALESCE(tu.notification_level,1) > :muted",
+            muted: TopicUser.notification_levels[:muted],
+          )
     end
 
     @all_topics = TopicQuery.remove_muted_tags(@all_topics, @guardian.user).includes(:last_poster)

spec/models/category_list_spec.rb

@@ -43,6 +43,13 @@ RSpec.describe CategoryList do
       SiteSetting.default_tags_muted = muted_tag.name
       Fabricate(:topic, category: public_cat, tags: [muted_tag])
 
+      muted_tag_2 = Fabricate(:tag)
+      TagUser.create!(
+        tag: muted_tag_2,
+        user: user,
+        notification_level: TagUser.notification_levels[:muted],
+      )
+
       CategoryFeaturedTopic.feature_topics
 
       expect(