Initialize before use struct user_pass in ui_reader()

Initialize before use struct user_pass in ui_reader()

This was missed in commit 3512e8d3ad
Also add a comment to clarify how pem_password_callback is accessed
in ui_reader().

Change-Id: I82835ff8e1e31e067efd81bfb6e8cd19ee004d9c
Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20240908224220.478684-1-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg29114.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>