edit_line draws outside fixed-height stack boundary

[Joel Fernandes]

I noticed the edit_line widget draws outside of its stack boundary,
and on a scroll, overflows above the stack.

Code:
Shoes.app do
  para 'some text outside stack'
  stack :height => 200, :scroll => true do
    10.times do |i|
       edit_line "Edit line " + i.to_s
    end
  end
end


Joel