L1CaloFEXByteStream: Fix out-of-bounds array accesses.
Unused fibers are marked with *_NFI[i] == -1. Need to skip those rather than trying to use that as an index. Solves crashes seen when building with -D_GLIBCXX_ASSERTIONS.
Unused fibers are marked with *_NFI[i] == -1. Need to skip those rather than trying to use that as an index. Solves crashes seen when building with -D_GLIBCXX_ASSERTIONS.