Using a weak id delegate property will crash during instantiation of NIB on OS X 10.7

When adding SUUpdater in IB (in the NIB) and making a reference from the SUUpdater delegate to a ViewController will crash on OS X 10.7 because the delegate is a weak property.

Crash report:

	objc[308]: garbage collection is OFF
	objc[308]: cannot form weak reference to instance (0x7fc55b481cf0) of class MainWindowViewController
	
	Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
	0   libobjc.A.dylib               	0x00007fff97cb5768 _objc_trap + 4
	1   libobjc.A.dylib               	0x00007fff97cb58aa _objc_fatal + 195
	2   libobjc.A.dylib               	0x00007fff97cc14ad weak_register_no_lock + 346
	3   libobjc.A.dylib               	0x00007fff97cc1a59 objc_storeWeak + 360
	4   com.apple.CoreFoundation      	0x00007fff8d49770d -[NSObject performSelector:withObject:] + 61
	5   com.apple.AppKit              	0x00007fff8c7c5baa -[NSNibOutletConnector establishConnection] + 405
	6   com.apple.AppKit              	0x00007fff8c7c32a1 -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] + 1079
	7   com.apple.AppKit              	0x00007fff8c7b98bb loadNib + 322
	8   com.apple.AppKit              	0x00007fff8c7b8db8 +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] + 217
	9   com.apple.AppKit              	0x00007fff8c7b8cd3 +[NSBundle(NSNibLoading) loadNibFile:externalNameTable:withZone:] + 141
	10  com.apple.AppKit              	0x00007fff8c7b8c16 +[NSBundle(NSNibLoading) loadNibNamed:owner:] + 364
	11  com.apple.AppKit              	0x00007fff8ca29cd7 NSApplicationMain + 398
	12  com.VortexApps.NZBVortex3     	0x0000000100785f43 main + 275
	13  com.VortexApps.NZBVortex3     	0x000000010073e604 start + 52