You could use a transistor or a single inverter to invert the output state of the QT100A. Then the low level output of the QT100A, the state it defaults to, would make the light turn on.
You could use a 74AHC1G04 for the inverter. You would have to cut the track that goes from pin 1, the output, of the QT100A, and connect the output of the QT100A to the input of the 74AHC1G04. The output of the 74AHC1G04 would connect to whatever the QT100A used to connect to.
Power and ground of the 74AHC1G04 would connect to power and ground of the QT100A