FIX: site_contact_user should default to system user, not first admin user

lib/discourse.rb

@@ -272,7 +272,7 @@ module Discourse
   # Either returns the site_contact_username user or the first admin.
   def self.site_contact_user
     user = User.find_by(username_lower: SiteSetting.site_contact_username.downcase) if SiteSetting.site_contact_username.present?
-    user ||= User.admins.real.order(:id).first
+    user ||= (system_user || User.admins.real.order(:id).first)
   end
 
   SYSTEM_USER_ID ||= -1

spec/components/discourse_spec.rb

@@ -62,9 +62,9 @@ describe Discourse do
       expect(Discourse.site_contact_user).to eq(another_admin)
     end
 
-    it 'returns the first admin user otherwise' do
+    it 'returns the system user otherwise' do
       SiteSetting.stubs(:site_contact_username).returns(nil)
-      expect(Discourse.site_contact_user).to eq(admin)
+      expect(Discourse.site_contact_user.username).to eq("system")
     end
 
   end