Flate image and r1083565 (Was: Re: Walkers mass-test - help needed)

[Cyrille Berger]

Hello,

Now I have commited something that has the potential to break in stack 
operations. I have tested flatten image and it works (or at least, it works as 
good now as before, more below). I also have understood why we had issues in 
the paste when deleting shape, we have to be careful not to delete  
KisShapeLayer objects, since they are managed by a shared pointer (I am going 
to add assert on this).

But I have noticed a problem when flatening a shape layer:
* create new image
* add a shape
* flaten image
* undo

the shape is gone. But it happens before my change and in 2.1. Reported in 
[1]. If you have any other unexpected crash when manipulating the layer stack, 
please tell me. (actually it can be caused by Dmitry's walker change too, but 
it should be quick to know what change caused the problem ;) )

[1] https://bugs.kde.org/show_bug.cgi?id=225825

-- 
Cyrille Berger