[FIX] mail: don't check read access if user not connected.
[FIX] mail: don't check read access if user not connected.

In the worst case, user is not logged in and he will really have no access and
will have a perm read error after login. We cannot check if an unknow user has
access or not.

In most cases, user will be logged in and will see the document directly if
he has access or will be redirected to messaging if no access.

In the best case, he will be redirected to login page before to see the message.

task-22505

dfang/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,ygol/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,dfang/odoo,dfang/odoo,dfang/odoo,ygol/odoo