[FIX] crm: avoid crash when merging leads

- When merging leads that creates a partner, an error could be thrown
  due to the `res.partner` `default_get` method that reads values from the
  lead that creates the partner.
  The issue is due to the fact that the `crm.lead` record is merged (and
  unlinked), trying to read it will cause an error since the records
  doesn't exists anymore.

  This fix checks that the `crm.lead` we are trying to read from exists.

closes odoo/odoo#30895

0 files changed, 0 insertions, 0 deletions