Blind effect broken with jQuery UI 1.12 and IE 11

[mar10]

The fix #717 does not work with IE 11. (But looks Ok with Edge, FF, Chrome, and Safari).

It seems that this CSS rule is not honored by IE 11:

li.fancytree-animating {
	position: relative;
}

[mar10]

Adding an inline style while animation is running seems to solve it:

$(node.ul).parent().css("position", "relative");

[mar10]

Turned out that renderStatus resetted the fancytree-animating class