4.0 regression: SIGFPE since "packetizer: use date_Change()"

date_Change() can't be called on a date that is not initialized.

Here is a SIGFPE backtrace with an mlp sample:

[00007fff90000c40] main input debug: `file:///home/tom/Videos/4K_test_clips/LaLaLand_cafe_4K.mkv' successfully opened
[00007fff90000c40] main input debug: Buffering 0%
[00007fff88ced930] mlp packetizer: MLP channels: 8 samplerate: 48000
[00007fff90000c40] main input debug: Buffering 13%
[00007fff90000c40] main input debug: Buffering 14%
[00007fff90000c40] main input debug: Buffering 27%
[00007fff90000c40] main input debug: Buffering 41%

Thread 46 "vlc" received signal SIGFPE, Arithmetic exception.
[Switching to Thread 0x7fffbbae8700 (LWP 25910)]
0x00007ffff794857d in date_Change (p_date=p_date@entry=0x7fff88c0e6b8, i_divider_n=48000, i_divider_d=i_divider_d@entry=1) at ../../src/misc/mtime.c:90
90	    p_date->i_remainder = p_date->i_remainder * i_divider_n / p_date->i_divider_num;
(gdb) bt
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x00007ffff794857d in date_Change (p_date=p_date@entry=0x7fff88c0e6b8, i_divider_n=48000, i_divider_d=i_divider_d@entry=1) at ../../src/misc/mtime.c:90
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x00007fff7c4a2c0e in Packetize (p_dec=0x7fff88ced930, pp_block=0x7fffbbae7d18) at ../../modules/packetizer/mlp.c:430
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x00007ffff78fc46c in DecoderProcess (p_dec=p_dec@entry=0x7fff88ced100, p_block=p_block@entry=0x7fff88c1bb10) at ../../src/input/decoder.c:1380
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x00007ffff78fc9bf in DecoderThread (p_data=<optimized out>) at ../../src/input/decoder.c:1615
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x00007ffff6e7f5aa in start_thread (arg=0x7fffbbae8700) at pthread_create.c:463
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x00007ffff69b0cbf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
(gdb) print p_date->i_divider_num
$1 = 0
(gdb) 

added Severity::normal Type::bug Version::master git + 1 deleted label

changed milestone to %4.0

regression, date_change usage has always been checked due to previous issues...

assigned to @Courmisch and unassigned @MigrationBot

Fixed by 3667d57b

added Status::fixed label

closed