Pricelist : Error when context['date']=False

In product/pricelist.py, if you enter the function price_get_multi() with context['date'] = False or None, you will have an error message :
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At least one pricelist has no active version ! Please create or activate one.
>>

For example, one scenario where you enter the function function price_get_multi() with context['date'] = False or None is when you use the module "product_visible_discount" :

in product_visible_discount.py line 87, inside the function product_id_change() you have :

list_price = pricelist_obj.price_get(cr, uid, [pricelist], product.id, qty or 1.0, partner_id, {'uom': uom,'date': date_order })
(the function price_get() calls price_get_multi())

and the default value for the variable "date_order" is False, as you can see in the proto of the function product_id_change().

I think that the proper fix for this is simply to test if context['date'] has a value before using it for the 'date' variable in the function price_get_multi() in product/pricelist.py. My merged proposal that will be attached to this bug implements this fix.