[ESS] drop empty help buffers

[Sam Steingold]

> * Sam Steingold <fqf at tah.bet> [2012-02-10 13:39:36 -0500]:
>
> when I do C-c C-v (ess-display-help-on-object) or "?mi" in *R*, I get
> a help buffer with
> ==============
> No documentation for 'mi' in specified packages and libraries:
> you could try '??mi'
> ==============
> I think it would be better if no new buffer were created and the error
> message was shown in the echo area (aka minibuffer), just like when I do
> M-x manual-entry RET zzz RET
> I do not get an empty *Man* buffer but a message "Can't find the zzz manpage".

this is repeated in the official user RFE file rsn.txt:

Ross Boylan:

I wish that ?foo, where foo is a non-existent
command, didn't leave a *help[R](foo)* buffer lying around.

yet, actually, it has already been implemented: just customise
ess-help-kill-bogus-buffers to t.

-- 
Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X 11.0.11004000
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