project_scrum has cron issues on v16

[risto42]

Module

project_scrum

Describe the bug

A clear and concise description of what the bug is.

To Reproduce

v16

viewing the logfile, the following is displayed:

Traceback (most recent call last):
  File "/opt/odoo/odoo/addons/base/models/ir_cron.py", line 391, in _callback
    self.env['ir.actions.server'].browse(server_action_id).run()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/odoo/odoo/addons/base/models/ir_actions.py", line 652, in run
    self.env[action.model_name].check_access_rights("write")
    ~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/opt/odoo/odoo/api.py", line 550, in __getitem__
    return self.registry[model_name](self, (), ())
           ~~~~~~~~~~~~~^^^^^^^^^^^^
  File "/opt/odoo/odoo/modules/registry.py", line 186, in __getitem__
    return self.models[model_name]
           ~~~~~~~~~~~^^^^^^^^^^^^
KeyError: 'project.sprint'