[IMP] hr: Default employee gender should be null rather than male

Purpose of the task is, when creating a new employee, the default
gender should be empty.

closes odoo/odoo#42843

Taskid: 2165484
Closes: #42843
Related: odoo/enterprise#7648
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

addons/hr/models/hr_employee.py

@@ -52,7 +52,7 @@ class HrEmployeePrivate(models.Model):
         ('male', 'Male'),
         ('female', 'Female'),
         ('other', 'Other')
-    ], groups="hr.group_hr_user", default="male", tracking=True)
+    ], groups="hr.group_hr_user", tracking=True)
     marital = fields.Selection([
         ('single', 'Single'),
         ('married', 'Married'),