lalpulsar_MakeSFTs "nosfts" file not handled properly with HTCondor file transfer

lalpulsar_MakeSFTDAG.py writes the SFT file names to transfer and where they should go (via remap) but if a user has specified --allow-skipping=True and the channel is not present or have a high enough sampling frequency, then a 0-byte nosfts file is written instead of an SFT for that channel. We need a way to deal with this potential issue, mostly for the Fscan workflow