Very minor fix for PIXELVALID derivation, where only two changes are applied for (int) => (uint64_t).
This shouldn't change any result.
We wish to use this fix for further reprocessing for Pixel detector study. Especially, this is quite important for RUN-3, and pixel detector simulation. Here, we want to activate the radiation damage effect in simulation for RUN-3.
This fix is necessary to validate the tracking efficiency and possible bias on the positioning resolution.