When Squeak changes from 3.x to next 3.x , I check my old projects still
works .
I found following is failing as miMorph formerPosition returns nil

acceptDroppingMorph: miMorph event: evt
    | centro |
    "When pieces are dropped into board, here you check if the center of
correct place is inside the piece and if true stick it in place"
miMorph class = PiezaSelectionMorph ifTrue: [miMorph submorphsDo: [ :m |
self  acceptDroppingMorph: m event: evt ].
miMorph delete.

] ifFalse: [
    centro := centrosXY at: miMorph numero.
    (miMorph containsPoint: centro)
        ifTrue: [SampledSound playSoundNamed: 'clink'.
            miMorph center: centro.
            miMorph borderColor: Color red.
            miMorph sticky: true.
            self addMorphFront: miMorph.
            self fin]
        ifFalse: [miMorph position: miMorph formerPosition.
            miMorph openInWorld]]

In Squeak3.8g-6548.image is workning and in newer not, so I wish a clue what
update could causing this and if is really a bug what I should report to
Mantis

Thanks in advance.

Edgar

PD. The .sar is in http://minnow.cc.gatech.edu/squeak/3938 "Rompecabezas"