[calligra] krita/ui: don't even try to merge if there's nothing to merge

[Boudewijn Rempt]

On Saturday 25 February 2012 Feb, Dmitry Kazakov wrote:
> Probably, we should be more accurate and not to check
> !layer->prevSibling(), but introduce functions like prevLayer(). Because
> this check doesn't cover the case when masks and layers are mixed.

Possibly... This is the same check as is done in KisImage::mergeDown. I'm reluctant to add new api right now, though. At the moment, when merging down a loayer, all masks are discarded anyway.

-- 
Boudewijn Rempt
http://www.valdyas.org, http://www.krita.org, http://www.boudewijnrempt.nl