FIX: Only seed general category on new sites (#18130)

* FIX: Only seed general category on new sites

If the site already has human users (users with an id > 0) don't seed
the categories.

Follow up to: a6ad74c759

* use human_users scope

lib/seed_data/categories.rb

@@ -128,6 +128,8 @@ module SeedData
     end
 
     def should_create_category?(category_id, force_existence)
+      return false if User.human_users.any?
+
       if category_id > 0
         force_existence ? !Category.exists?(category_id) : false
       else

spec/lib/seed_data/categories_spec.rb

@@ -93,6 +93,22 @@ RSpec.describe SeedData::Categories do
       end
     end
 
+    it "does not seed the general category for non-new sites" do
+      Fabricate(:user) # If the site has human users don't seed
+
+      expect { create_category("general_category_id") }
+        .to not_change { Category.count }
+        .and not_change { Topic.count }
+    end
+
+    it "seeds the general category for new sites" do
+      expect { create_category("general_category_id") }
+        .to change { Category.count }
+        .and change { Topic.count }
+
+      expect(Category.last.name).to eq("General")
+    end
+
     it "does not override permissions of existing category when not forced" do
       create_category("lounge_category_id")