Levente Uzonyi uploaded a new version of System to project The Trunk:
http://source.squeak.org/trunk/System-ul.431.mcz

==================== Summary ====================

Name: System-ul.431
Author: ul
Time: 15 April 2011, 11:57:51.455 pm
UUID: 873b4f7f-6daa-d549-b8c1-55ffa1581e63
Ancestors: System-nice.430, System-fbs.427

Merged.

=============== Diff against System-nice.430 ===============

Item was changed:
  ----- Method: SystemNavigation>>spawnHierarchyForClass:selector: (in category 'browse') -----
  spawnHierarchyForClass: aClass selector: aSelector
  	"Create and schedule a new class hierarchy browser on the requested class/selector."
  	"SystemNavigation default spawnHierarchyForClass: SmallInteger selector: #hash"
  
  	(aClass == nil)  ifTrue: [^ self].
+ 	^ ToolSet browseHierarchy: aClass selector: aSelector
- 	ToolSet browseHierarchy: aClass selector: aSelector
  !