demux: mp4: ensure to load fragmented index
demux: mp4: ensure to load fragmented index

Could be skipped as we stop parsing on moov
and index can live between moov and moof

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc