title: Computed field on a tree view in odoo 13
body: <p>in customize module in odoo
  I add computed field transactions_count
  This field appears correctly in the form view
  But in the tree view it appears incorrectly (if its value is zero, it shows the value of the previous record)</p>
  <p>this is my code :</p>
  <pre><code>transactions_count = fields.Float(string='Total Amount', compute='_compute_transactions_ids')
  
  
  @api.depends('transactions_ids')
  def _compute_transactions_ids(self):
      amount = 0.0
      for order in self:
          for line in order.transactions_ids:
              amount = amount+ line.amount_total
          order.transactions_count = amount
  </code></pre>