next-window: error if there is none

[Drew Adams]

Just a question. Is this the behavior we want for next-window?

emacs -Q
M-: (next-window t)

Debugger entered--Lisp error: (wrong-type-argument window-live-p t)
  next-window(t)
  eval((next-window t))
  eval-expression((next-window t) nil)
  call-interactively(eval-expression)

I'm just wondering if it shouldn't perhaps return nil if there is no next
window.