"transitionend" not firing if element not displaying (FireFox)

[dovid]

Perhaps a bit of an uncommon situation, but does seem to cause an issue in handleHide()

https://bugs.webkit.org/show_bug.cgi?id=51945

[BlackGlory]

I have a similar issue in Chrome 52.0.2743.82 m (64-bit), "transitionend" not fire sometimes.

It seems like could solved by use this.loadingBox.style.opacity = 0.01; instead of this.loadingBox.style.opacity = 0;, worked for me.