Hi!

I guess not too many use ProportionalSplitters to change the layout of
windows these days, but they are broken in the latest trunk image.
This is because the Method containingWindow in Morph has changed. The
containing Window is now searched based on the model of the component,
but ProportionalSplitters do have no model.
A quick fix is to look up the owner chain of a ProportionalSplitter to
find an owner that has a model. Most of the time (always?) the owner
will be the containing window, so I don't know if the ifFalse: Branch
is needed.
I will publish this fix so ProportionalSplitters should work again
until someone with better insights has a better solution.

Alex