Draggable.hitTest() trhows and error when it can't find the element:
Cannot read property 'getBoundingClientRect' of null
I found the line with _unwrapElement(e).getBoundingClientRect() in Draggable.js and fix it like that:
_unwrapElement(e) ? _unwrapElement(e).getBoundingClientRect() : false
It just returns false when there is no element or it's hidden. Everything is working now but on my side. I'm not sure that this is the right fix. I will try to reproduce the problem on codepen when I have more time if you are not aware of this behavior.