bug#3192: 23.0.92; disabling tooltip-mode inhibits showing Customize error msgs

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> emacs -Q
>  
> (defcustom foo nil
>   "..."
>   :type '(alist :key-type (symbol) :value-type (function)))
>  
> M-x customize-option foo
>  
> Edit the Function field to nil (which is an invalid value).
> Click the State button and choose Set for Current Session.
>  
> You see the message "Invalid function: nil" in the echo area.
>  
> M-x tooltip-mode (to turn it off)
>  
> Click the State button again and choose Set...
>  
> No message is displayed. The message is logged in *Messages*, but the
> user sees nothing to indicate what, if anything, happened.

I can't reproduce this, either with Emacs 23 or trunk.