'From Squeak3.7beta of ''1 April 2004'' [latest update: #5923] on 25 May 2004 at 3:41:49 pm'! "Change Set: registeredFlapsQuadsAt-fix-mu Date: 24 May 2004 Author: Masashi Umezawa Flaps>>registeredFlapsQuadsAt: assumes (self environment at: className) returns nil. It is apparently wrong. This patch checks class existence using includesKey:. "! !Flaps class methodsFor: 'flaps registry' stamp: 'mu 5/24/2004 20:30'! registeredFlapsQuadsAt: aLabel "Answer the list of dynamic flaps quads at aLabel" ^ (self registeredFlapsQuads at: aLabel) removeAllSuchThat: [:q | (self environment includesKey: q first) not] ! !