re-open invoice assigned to useability/no one

observed in v6 and trunk.

Use case: I want to be able to cancel invoices and invoice payments. To do so, I install account_cancel, and then configure the sales journal and the bank journal to allow cancelling entries. I make an invoice and pay it. Then I want to change something in the invoice. So first I unreconcile the voucher, then I should be able to set the invoice back to "open" and then also to cancel it.

There is a button in the view, but for some reason it is assigned to "useability-no one" group, so no one can see it.

for trunk, see:
http://bazaar.launchpad.net/~openerp/openobject-addons/trunk/view/head:/account/account_invoice_view.xml#L218

and for v6, same thing:
http://bazaar.launchpad.net/~openerp/openobject-addons/6.0/view/head:/account/account_invoice_view.xml#L217

I suggest to change that group to something else, like accounting/manager.

Thanks!