Bug Backward compatibility mDataProp 1.9.2 to 1.9.4

Hi allan,

I found a small Bug when I upgrade to 1.9.4
Below 2 jsfiddle

1.9.2 : http://jsfiddle.net/HEDvf/198/
1.9.4 : http://jsfiddle.net/HEDvf/199/

In the second there is an alert .

I've already fix the source code.

https://github.com/DukeAstar/DataTables/commit/d9bb6b63cd5f5f8ab692ba0e1913a56b0772ae2c