What is the correct way to call a modal window inside another modal in Bootstrap?

Question

Bootstrap

There is a modal window, for example, Authorization, inside it there is a Registration link, when clicked, the current modal should close and the registration modal should open. Achieved this with this design:

<a href="#" data-dismiss='modal' data-toggle="modal" data-target="#signup-modal">Регистрация</a>

but in this case, a jamb appears: when switching to the second modal window, a scroll appears for the main page, because of this, it is not possible to scroll the modal directly and it is cut off at the bottom.
Example on CodePen