only clear caches if we are actually connected to the database

activerecord/lib/active_record/railtie.rb

@@ -149,11 +149,13 @@ class Railtie < Rails::Railtie # :nodoc:
 
       ActiveSupport.on_load(:active_record) do
         ActionDispatch::Reloader.send(hook) do
+          if ActiveRecord::Base.connected?
             ActiveRecord::Base.clear_reloadable_connections!
             ActiveRecord::Base.clear_cache!
           end
         end
       end
+    end
 
     initializer "active_record.add_watchable_files" do |app|
       path = app.paths["db"].first