Sortable: cancel method called during sort fails if revert option is set

[jpevarnek]

​http://jsfiddle.net/cxjXM/ (repro notes in the fiddle)

The problem appears to be that cancel clears out this.helper (line 487) while adding a callback to _clear for after the animation finishes (line 445). _clear then fails when attempting to access this.helper (line 1176).

[tj.vantoll]

I can confirm this behavior and that it only occurs when the revert option is set.

The cancel method still works with the revert option if called in a stop or receive event - ​http://jsfiddle.net/tj_vantoll/e6hwT/.

I'm not sure that canceling a sort during a drag is a supported use of the cancel method, but this seems like a legit use case so I'll mark this as valid for now.

[jpevarnek]

Just a quick note regarding this being a supported use case, the code from the fiddle was taken pretty much exactly from a developer comment in #5055

[Scott González]

Canceling a sort is bad UX and will be removed in a future version. With that in mind, we're not likely to spend any time trying to fix this, but we're more than happy to review a pull request from the community.