There is a bug in webcore where it cannot process users from slots 0 or 1 which is why you see NULL. The only solution is to assign users in slot 2 or greater to use webcore as explained in this post.
Unfornately Smart locks cannot do that, it doesn’t allow you to select the slot numbers. For doing that you will need a app like LUM to assign specific users to specific slots: [RELEASE] Lock User Management (LUM)