Transition: Disable animationEnd callback on transition reset.

[dos1]

Fixes rare race condition with modals where animationEnd callback on dimmer could fire before modal's one, calling .transition('reset') on modal right before animationEnd event for it arrives, causing module.complete callback to restore incorect conditions, making modal visible when it shouldn't be, causing next modals to misbehave.

[jlukic]

Cautiously merging this, luckily only modal is using transition reset currently, so regression possibilities are minimal.

Previously we used a fix like this which made sure there were no race conditions.

But after transition rewrite, I thought this bug would be gone since I could not reproduce.

[dos1]

It's actually similar, but different bug - this one is harder to trigger and instead of closing modal without closing the dimmer, it makes previous modal to not close at all (transition module thinks it's already hidden, but modal and dimmer think it's still there).

After .transition('reset') the modal was made hidden (correct), but when animationEnd arrived after that, it was made visible again (wrong). It seems to me like it's rather caused by the browser than race condition in the code, as I'd think that after reset this callback shouldn't actually arrive at all.

On one PC I could reproduce this one easily by dragging the tab out of window approximately the same time animations were about to finish, but on the other one it required many tries to trigger it. I wasn't able to reproduce it by modifying Semantic code to change the order of called instructions manually, so again, it smells to me like a "race condition" in the browser, which reports animationEnd callback for animation that was already cancelled right before that (which when I think about it may be explained by JS thread being separated from rendering threads in modern browsers - event may be already queued to be triggered when animation is reseted, so it will be called only when JS thread is back to event loop)

I hope I'm not too hard to understand :D The commit message has already revealed my tendency to make overly complicated sentences ;)

[jlukic]

Your fix landed in 0.12.1. Seeing as reset is only called when using modal, and it appears to fix the issue in your testing. I trust that it will be fine.

My only concern was about breaking queueing which uses animationEnd to trigger the next queued animation.