Instabilitity probably due to inform:during:

[StéphaneDucasse]

I get diffPanel is nil in subclasses

IceTipPreviewBrowser>>initializePresenters

	self application 
		informUser: 'Calculating diff'
		during: [ diffPanel := self instantiate: IceTipDiffPanel on: self model diff ].
	actionPanel := self newButtonBar.
	actionPanel add: (button := self newActionButton)

And I suspect the during: to not being executed at the right moment.

[Esteban Lorenzano]

we reverted the change so now this does not happens anymore