NoMethodError: undefined method `first' for nil:NilClass

If action_pack version is 3.0.x, then raise NoMethodError: undefined method `first' for nil:NilClass.

Rails version is 3.0.9.

You can see [here](https://github.com/shadabahmed/logstasher/blob/master/lib/logstasher/rails_ext/action_controller/metal/instrumentation.rb#L8).