Custom UI button layout reverts to default when riding an entity

UI buttons placed at the topmost possible position reverts to their default position when riding entities.

Specifically, when any of the UI buttons are positioned where they are touching the red area on the edit menu, saves it, and then the player attempts to ride a rideable mob, the UI buttons will revert to their default position and size. Otherwise, buttons not touching the red area on the edit menu retain their position and size.