It is of no value to the user, because every muxer can always
be flushed with a NULL packet. As its documentation shows
("If not set, the muxer will not receive a NULL packet in
the write_packet function") it is actually an internal flag
that has been publically exposed because there was no internal
flags field for output formats for a long time. But now there is
and so use it by replacing the public flag with a private one.
Reviewed-by: James Almer <jamrial@gmail.com>
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>