Unable to create purchase from purchase_request with empty description and no supplier
The purchase request wizard compares the request description with the wizard description in order to determine which purchase request to update.
But this does not work well as the clients sends '' instead of None for the description values making the comparision fail [1]
I'm not sure if we should fix it on server side, or at client side.
[1] http://hg.tryton.org/modules/purchase_request/file/tip/purchase_request.py#l383
[1]