Bug: slot.clear crash, but only in Shoes subclasses. v0.r873, OS X

[Edward Heil]

OS X, Shoes v0.r873.

Clicking this button does not crash Shoes.

Shoes.app do
  stack do
    @emptystack = stack
    button "Unempty empty stack...." do
      @emptystack.clear { para "emptystack is no longer empty" }
    end
  end
end


Clicking this button crashes Shoes:

class Bug < Shoes
  url '/', :main
  def main
    stack do
      @emptystack = stack
      button "Unempty empty stack...." do
        @emptystack.clear { para "emptystack is no longer empty" }
      end
    end
  end
end
Shoes.app