NSOutlineView initialization and -itemAtRow: patch

[Quentin Mathé]

Hi,

Here is a patch that corrects -itemAtRow: to return nil when no row  
exists for the given index (that's Cocoa behavior).
This patch also tries to clean the initialization of NSOutlineView  
since the ivars aren't initialized to the same values when you create  
the outline view in Gorm or in code by calling -initWithFrame:. For  
example, setting _indentationForLevel by default isn't really useful.  
Precisely -initWithFrame: sets the value to zero when -initWithCoder:  
sets it to 10. On Cocoa side, the value is equal to 16 in both cases.
NSTableView tries to share initialization code in a similar way with - 
_initDefaults. However I have been unable to find an interface  
declaration for -_initDefaults, I suppose there is one somewhere?…  
because the compiler doesn't produce any warnings for NSTableView. I  
mention this, because in the patch -_initOutlineDefaults is a bit far  
away from -initWithFrame: unlike -_initDefaults in NSTableView.m. I  
think it would be better to keep these methods rather close.

NSOutlineView.m.patch
Description: Binary data

Cheers,
Quentin.