This was removed in CanJS (which replaces jQueryMX in JMVC 3.3). I created an issue here to add something like this back. If you want to see this added to CanJS, comment on the issue and add your support. That's one of the main ways we know what features to prioritize.
In the mean time, you could check if this.element === null, which only happens when a Control instance is destroyed.