Crash on returning picking

Hello,

crash appear in OpenERP 6.1, when opening the return wizard on picking which has lines that are not done (cancelled for example). Code line: stock/wizard/stock_return_picking.py:75 (http://bazaar.launchpad.net/~openerp/openobject-addons/6.1/view/head:/stock/wizard/stock_return_picking.py#L75)

Code line:
return_history = self.get_return_history(cr, uid, record_id, context)

get_return_history adds only "done" lines to the dictionary, and default_get method tries to get all of the lines from it:

for line in pick.move_lines:
                qty = line.product_qty - return_history[line.id]

In OpenERP 7.0 it adds all the lines (using "qty = line.product_qty - return_history.get(line.id, 0)"), I'm not sure if this is correct way, since how can you return products that are cancelled. I would suggest to add those products to wizard, but with quantity 0, for not to go far from current logic.