A new version of Monticello was added to project The Inbox:
http://source.squeak.org/inbox/Monticello-kfr.617.mcz

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

Name: Monticello-kfr.617
Author: kfr
Time: 20 May 2015, 8:08:51.778 pm
UUID: 0e759ace-d543-f340-a3c2-82dedb54f38d
Ancestors: Monticello-cmm.616

Sometimes stepChilden is nil.

=============== Diff against Monticello-cmm.616 ===============

Item was changed:
  ----- Method: MCAncestry>>stubAncestryFor:using: (in category 'initialize-release') -----
  stubAncestryFor: aMCWorkingCopy using: aMCRepository 
  	"childInfo was retrieved from aMCRepository.  Replace my ancestry with a Proxy that can retrieve the full tree from these two elements."
  	ancestors := ancestors collect:
  		[ : each | each isMCInfoProxy
  			ifTrue: [ each ]
  			ifFalse:
  				[ MCInfoProxy
  					info: each copyWithTrimmedAncestry
  					workingCopy: aMCWorkingCopy
  					repository: aMCRepository ] ].
+ 	stepChildren := stepChildren ifNotNil:[ :collection | collection collect:
- 	stepChildren := stepChildren collect:
  		[ : each | each isMCInfoProxy
  			ifTrue: [ each ]
  			ifFalse:
  				[ MCInfoProxy
  					info: each copyWithTrimmedAncestry
  					workingCopy: aMCWorkingCopy
+ 					repository: aMCRepository ] ]]!
- 					repository: aMCRepository ] ]!