Offline contribution receipt_date value of email

The receipt_date value of email in offline contribution is set to the "Receipt Date" input field value.
However, the field will become hidden if you tick the "Automatically email a receipt for this contribution to test@example.org?" check box.

It should be set to the current date. Then in the "Contributions - Receipt (off-line)" message template, we can use "$receipt_date" variable.