Fix for crashes for ofxFaceTrackerThreaded in iOS and slower machines.

-While it was working fine in OSX and Windows I have tracked down a
constant crash for when working on iOS to the setup routine not
completing before the rest of the app query’s the tracker.
-This may also happen on older / slower machines or with a slow HDD.
-Fix proposed just returns the default datatype as was setup (stops
null vector crashes etc).