Numbering of draft buffers

[Markus Huber <markus.huber@informatik.uni-augsburg.de>]

After updating to wl 20140515, I get errors saying

"byte-code: Format specifier doesn't match argument type"

whenever I try to reply - with or without citation - to a message
or forward one. If I start a new mail the error does not show
up. However in any of the four cases the numbering and renaming
of draft buffers does not work. Downgrading to 20140210 fixes the
issue.

Debugger entered--Lisp error: (error "Format specifier doesn't match argument type")
  signal(error ("Format specifier doesn't match argument type"))
  byte-code("\302!\210\303	@	A\"\207" [winconf err set-window-configuration signal] 3)
  wl-summary-reply(nil t)
  wl-summary-reply-with-citation(nil)
  call-interactively(wl-summary-reply-with-citation nil nil)

Any ideas on why this might be and/or how I can debug what's going on?

Cheers,

Markus