Double clicking on arrow with lazy-load causes assertion error

[Bringer128]

Example JSFiddle:
http://jsfiddle.net/tasn7jzg/1/

To reproduce in the above fiddle, either double-click on the arrow in the node or click the "Cause error" button which does two clicks with JQuery synchronously.

The problem:
Double clicking on the arrow (class="fancytree-expander") with lazy-loading enabled causes a race condition, where the 2nd click occurs before the first lazy-loaded request completes. This logs an error in the console and fires any window.onerror handlers in the consuming application's UI.

This happens fairly regularly as expanding a node can be done by clicking the arrow once, or by double-clicking any of the other elements in the containing span. As people double-click to expand they occasionally miss the text or icon and hit the arrow.

[Bringer128]

That was quick, thanks!

[mar10]

No problem. Your description and fiddle helped to fix it. Thanks for contributing!