Error trying to find warehouse_id when point_of_sale is not installed

[Yajo]

Install sales module, then try to make a quotation or sales order. Create a line with a product. Then, press in the little button at the right of the product name (the arrow exiting from the box) to open its form. OpenERP throws this:

OpenERP Server Error

Client Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 204, in dispatch
    response["result"] = method(self, **self.params)
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/controllers/main.py", line 1128, in call_kw
    return self._call_kw(req, model, method, args, kwargs)
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/controllers/main.py", line 1114, in _call_kw
    records = req.session.model(model).read(*args, **kwargs)
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 42, in proxy
    result = self.proxy.execute_kw(self.session._db, self.session._uid, self.session._password, self.model, method, args, kw)
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 30, in proxy_method
    result = self.session.send(self.service_name, method, *args)
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 103, in send
    raise xmlrpclib.Fault(openerp.tools.ustr(e), formatted_info)

Server Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 89, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/usr/lib/pymodules/python2.7/openerp/netsvc.py", line 296, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/usr/lib/pymodules/python2.7/openerp/service/web_services.py", line 626, in dispatch
    res = fn(db, uid, *params)
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 190, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 132, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 199, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 187, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/usr/lib/pymodules/python2.7/openerp/osv/orm.py", line 3679, in read
    result = self._read_flat(cr, user, select, fields, context, load)
  File "/usr/lib/pymodules/python2.7/openerp/osv/orm.py", line 3788, in _read_flat
    res2 = self._columns[val[0]].get(cr, self, ids, val, user, context=context, values=res)
  File "/usr/lib/pymodules/python2.7/openerp/osv/fields.py", line 1145, in get
    result = self._fnct(obj, cr, uid, ids, name, self._arg, context)
  File "/usr/lib/pymodules/python2.7/openerp/addons/stock/product.py", line 357, in _product_available
    stock = self.get_product_available(cr, uid, ids, context=c)
  File "/usr/lib/pymodules/python2.7/openerp/addons/stock/product.py", line 218, in get_product_available
    warehouse_id = shop_obj.read(cr, uid, int(context['shop']), ['warehouse_id'])['warehouse_id'][0]
KeyError: 'warehouse_id'

It doesn't make sense because there was no configuration of several warehouses or shops. I had to install those modules and configure it and install point_of_sale to fix this, but those are unnecessary for my business.