CUser::Update how to update data without password?

Question

1C-Bitrix

Hello.
I have a form on a website. I need to update user data. I do it through the CUser::Update function. It has the required fields password and confirm_password
The form has fields for a new password, but they can be empty.
Question: How to get the user's old password in order to pass it to the function if the new password was not set? Or can you advise how to do it right