* parse.y (reduce_nodes): empty body should return nil.

Curious, but what was this meant to solve?

Here is how it looks via ParseTree now:

> <514> echo "class Example; def empty; end; end" | parse_tree_show
> [[:class,
>   :Example,
>   :Object,
>   [:defn, :empty, [:scope, [:block, [:args], [:nil]]]]]]

Is it now the case that every method will leave something on the stack? 
Can we assert that in our tests?