#6 prepare_audio.sh fails if mythburn.log contains binary chars

[Torsten Crass]

On one occasion (recording of "Chocolat" on German TV,
around Easter -- this recording contained 3 audio
tracks), prepare_audio.sh didn't yield any output,
leading to a final DVD withoug any sound. I tracked
down the issue to the two grep commands in lines 24 and
25 of prepare_audio.sh. Running them manually on the
corresponding mythburn.log led to a message like
"expression matches on binary file mythburn.log" (don't
remember exactly). This could be resolved by explicitly
showing any non-printable characters from mythburn.log
by bassing it through "cat -v".

Resolution: Insert

cat -v ${logifle} > mythburn.log.tmp
rm mythburn.log
mv mythburn.tmp.log mythburn.log

somewhere before the grep commands.