1) Fixed a mistake where it fired exceptions when clicking on TUIOs, because
the value was empty for a short period of time causing it to parse an
empty value to a string.
2) Fixed a mistake where it tried to move the TUIO with the id 0 in the
TUIOMouseListener, which is the value it gets when you try to drag nothing
i.e. trying to drag the background and thus not having a TUIO in focus.