Error:
Hi I get this error, how can I fix this?
 I am facing the below error while upgrading the module 
Odoo Server Error
Traceback (most recent call last):
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_http.py", line 237, in _dispatch
    result = request.dispatch()
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 683, in dispatch
    result = self._call_function(**self.params)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 359, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\service\model.py", line 94, in wrapper
    return f(dbname, *args, **kwargs)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 347, in checked_call
    result = self.endpoint(*a, **kw)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 912, in __call__
    return self.method(*args, **kw)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 531, in response_wrap
    response = f(*args, **kw)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\web\controllers\main.py", line 1381, in call_button
    action = self._call_kw(model, method, args, kwargs)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\web\controllers\main.py", line 1369, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\api.py", line 396, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\api.py", line 383, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "", line 2, in button_immediate_upgrade
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_module.py", line 73, in check_and_log
    return method(self, *args, **kwargs)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_module.py", line 653, in button_immediate_upgrade
    return self._button_immediate_function(type(self).button_upgrade)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_module.py", line 592, in _button_immediate_function
    modules.registry.Registry.new(self._cr.dbname, update_module=True)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\modules\registry.py", line 89, in new
    odoo.modules.load_modules(registry._db, force_demo, status, update_module)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\modules\loading.py", line 497, in load_modules
    env['ir.model.data']._process_end(processed_modules)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_model.py", line 2237, in _process_end
    record.unlink()
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_model.py", line 1357, in unlink
    self._process_ondelete()
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\addons\base\models\ir_model.py", line 1382, in _process_ondelete
    ondelete = (field.ondelete or {}).get(selection.value) or 'set null'
Exception
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 639, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "C:\Program Files\Odoo 14.0.20201228\server\odoo\http.py", line 315, in _handle_exception
    raise exception.with_traceback(None) from new_cause
AttributeError: 'str' object has no attribute 'get'
