file: improve messages when reading partitions
file: improve messages when reading partitions

Warn if header partition status is closed but the footer partition
offset is not set. Only warn about the missing footer partition
offset and RIP if the footer partition was found and read.

Limecraft/ebu-libmxfpp,stuarthicks/libmxfpp,Limecraft/ebu-libmxfpp,Limecraft/ebu-libmxfpp,stuarthicks/libmxfpp,stuarthicks/libmxfpp