[FIX] resource: Fail fast if no calendar
[FIX] resource: Fail fast if no calendar

The methods `get_work_hours_count` and `_attendance_intervals`
raise a traceback if `self` does not contain a single calendar record.

This commit adds an explicit check for this requirement.

Related PR odoo/enterprise#10593

closes odoo/odoo#51326

X-original-commit: e5d93be382b03c7a9c925b4a2e6be6875843195d
Related: odoo/enterprise#10619
Signed-off-by: Yannick Tivisse (yti) <200a91eb0e5cc4726d6a3430713b580138f34298@odoo.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo