Internal variables not updated when external remote used

[Marcus Karlsson]

When in tellstick.py deviceEvent the parameter data comes as NULL from tellstick-core callback, the int(data) throws exception leading up to that cv.save() is not executed.

The above has the effect that Live and Remote web page shows incorrect state when using physical remotes.

Can be fixed by adding: if str(data)=='': myData=0 else: myData=data

And use myData instead of data in line 41/43.