title: AttributeError: 'NoneType' object has no attribute 'get_default_company'
body: <pre><code>class Sale(osv.osv):
  _name = 'sale'
  
  _columns = {
      'name': fields.char('Company Name', size=128)
  }
  
  def get_default_company(self, cr, uid, context=None):
      company_id = self.pool.get('res.users').browse(cr, uid, uid).company_id.id,
      return company_id
  Sale()
  </code></pre>
  
  <p>I used above code , all is well but I don't know where and how to call my function <code>get_default_company()</code>. As when I call this method it's give </p>
  
  <pre><code>cr and uid invalids 
  </code></pre>