Error "ffl::ffl: the input frame file list has an unknown format" when the input ffl includes another ffl in addition to a list of frame files

For instance in /virgoData/ffl/V1Online.ffl:

/data/dev/hrec/V1KafkaO3ReplayMDC/longFiles.ffl 1363248000 1367568000
/data/dev/hrec/V1KafkaO3ReplayMDC/ShortFiles/V-V1_O3ReplayMDC_llhoft-1367568000-10.gwf 1367568000 10 1367568000 1367568010
(...) 

The simplest could be to replace internally the ffl line by the list of frame files it contains, and then to use the current code on this local "expanded" ffl.