UI can not be on/off if setting ui_visible false at initialization

[oUp2Uo]

Hi, after updating to the latest "lazy rendering" commit, if setting ui_visible (in file lib.rs) false at initialization, then key U would not work.
If ui_visible is true at the beginning, key U would be able to change UI showing on/off.

https://github.com/KeKsBoTer/web-splat/blob/master/src/lib.rs#L286

In last version, changing initial value of ui_visible would not effect key U event, which means both work fine.