Add missing <! in list case of awalk

[ojw]

Looks like the list? case in awalk is missing an outer <!.

Alternately, there's a case to do a bit more refactoring and pull the <! (and optionally even the <outer) out of the cond, which would also fix this.

For example, something like

(go
  (<! 
    (<outer
      (cond ...))))

I'm happy to write it up either way if you like, or of course you're welcome to close this and fix it in the style of your choosing.