Fix 'element not enabled' errors.
Fix 'element not enabled' errors.

The fact that the errors were occuring for the currentTarget made me
suspect I was somehow enabling the wrong element in my application, but
I've done a lot of testing and I'm 99% sure this is not actually
happening.

For more information, please see this post:
https://groups.google.com/forum/#!msg/cornerstone-platform/uU09JPyWJTU/1NhQXaMeBQAJ

chafey/cornerstoneTools,leonardorame/cornerstoneTools,HorizonPlatform/cornerstoneTools,leonardorame/cornerstoneTools,cornerstonejs/cornerstoneTools,google/cornerstoneTools,google/cornerstoneTools,swederik/cornerstoneTools,cornerstonejs/cornerstoneTools,cornerstonejs/cornerstoneTools,swederik/cornerstoneTools,HorizonPlatform/cornerstoneTools