don't try to load airbrake if there is no config for it

config/initializers/01-redis.rb

@@ -12,7 +12,7 @@ if defined?(PhusionPassenger)
         if forked
             # We're in smart spawning mode.
             $redis = DiscourseRedis.new
-            Discourse::Application.config.cache_store.reconnect# = DiscourseRedis.new_redis_store
+            Discourse::Application.config.cache_store.reconnect
         else
             # We're in conservative spawning mode. We don't need to do anything.
         end

config/initializers/airbrake.rb

@@ -0,0 +1,3 @@
+if Rails.env.production? && File.exists?(Rails.root + '/config/airbrake.rb')
+  require 'airbrake'
+end