Small rectangle in Mac browsers

[TraderStf]

Hello!

In Mac Safari, If I reduce the width of the window in the demo.html, I got a small rectangle at the bottom when you click on the menu icon (3 horizontal lines).

In Safari and Chrome, it appears immediately after clicking the icon.
In Firefox, you must enlarge then reduce the window after clicking the icon.

Capture from Safari.

Thanks for this nice framework.