DuckSay: Only call the function if there is an argument.

So the old implementation was that `ddg_spice_duck_say()` was getting called every time, and the problem with that is it gets executed first before reddit even gets back to us.

![screen shot 2014-09-25 at 1 23 09 pm](https://cloud.githubusercontent.com/assets/81969/4408964/c04f97f0-44d8-11e4-9ca3-3bfe183a60fa.png)

So we only call the function `ddg_spice_duck_say` without an argument if we're sure that we're not calling reddit.