Problem with mutable data.

[jzahorsky]

Hi.
I have a problem with class NSMutableData, concretly with the metod setData:.
When I create object
	obj = [NSMutableData data];
then [obj length]==0.  Then I call 
	[obj setData:aData]
and this metod generate critical error: 
	NSRangeException: in replaceBytesInRange:withBytes:, range {0,4} extends beyond size (0).
Is this problem in GNUstep implementation? 
	Jirka Z.