Fix crosstalk in FT

@bleverin @zexu @kreps

It seems to me that the loops that create XT photons are bugged in the current Boole implementation. Indeed, loops like

      for ( int tempiXTPhotons = 0; iXTPhotons < MAX_PHOTONS; iXTPhotons++ ) {

do not increment tempiXTPhotons and so sometimes never converge (and in any case never actually give the proper number of photons).

This should fix it.