## Description
There is a segment fault detected by AddressSanitizer

## System info
```
Ubuntu 20.04.2 LTS
clang version 12.0.0-++20210402082642+04ba60cfe598-1~exp1~20210402063359.71
MP4Box - GPAC version 1.1.0-DEV-rev1687-g16bd902cb-master
```

## Build command
```
./configure --static-mp4box --prefix=`realpath ./install` --enable-sanitizer --cc=clang --cxx=clang++
```

## crash command
```
MP4Box -frag 1 -out /dev/null poc_file
```

## Pocs
[poc.zip](https://github.com/gpac/gpac/files/7976877/poc.zip)


## Crash output
```
==15641==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x000000d776b8 bp 0x7ffea0e4f210 sp 0x7ffea0e4f0a0 T0)
==15641==The signal is caused by a READ memory access.
==15641==Hint: address points to the zero page.
    #0 0xd776b8 in mp4_mux_cenc_update /programs/mp4box/builds/build6/src/filters/mux_isom.c:3582:184
    #1 0xd6ab36 in mp4_mux_config_timing /programs/mp4box/builds/build6/src/filters/mux_isom.c:5863:6
    #2 0xd6ab36 in mp4_mux_process /programs/mp4box/builds/build6/src/filters/mux_isom.c:6033:3
    #3 0xb7c2ae in gf_filter_process_task /programs/mp4box/builds/build6/src/filter_core/filter.c:2515:7
    #4 0xb5d7eb in gf_fs_thread_proc /programs/mp4box/builds/build6/src/filter_core/filter_session.c:1756:3
    #5 0xb5c694 in gf_fs_run /programs/mp4box/builds/build6/src/filter_core/filter_session.c:2000:2
    #6 0x910850 in gf_media_fragment_file /programs/mp4box/builds/build6/src/media_tools/isom_tools.c:3816:6
    #7 0x4e6fcc in mp4boxMain /programs/mp4box/builds/build6/applications/mp4box/main.c:6455:7
    #8 0x7ff7959040b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #9 0x41ea6d in _start (/programs/mp4box/builds/build6/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /programs/mp4box/builds/build6/src/filters/mux_isom.c:3582:184 in mp4_mux_cenc_update
==15641==ABORTING
/collect/collec.sh: line 18: 15641 Aborted(core dumped)
------------------------
```
There is a segment fault detected by AddressSanitizer
This is a GitHub Issue
repo:gpac
owner:gpac
Title : There is a segment fault detected by AddressSanitizer
Issue date:

--- start body ---
## Description
There is a segment fault detected by AddressSanitizer

## System info
```
Ubuntu 20.04.2 LTS
clang version 12.0.0-++20210402082642+04ba60cfe598-1~exp1~20210402063359.71
MP4Box - GPAC version 1.1.0-DEV-rev1687-g16bd902cb-master
```

## Build command
```
./configure --static-mp4box --prefix=`realpath ./install` --enable-sanitizer --cc=clang --cxx=clang++
```

## crash command
```
MP4Box -frag 1 -out /dev/null poc_file
```

## Pocs
[poc.zip](https://github.com/gpac/gpac/files/7976877/poc.zip)


## Crash output
```
==15641==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x000000d776b8 bp 0x7ffea0e4f210 sp 0x7ffea0e4f0a0 T0)
==15641==The signal is caused by a READ memory access.
==15641==Hint: address points to the zero page.
    #0 0xd776b8 in mp4_mux_cenc_update /programs/mp4box/builds/build6/src/filters/mux_isom.c:3582:184
    #1 0xd6ab36 in mp4_mux_config_timing /programs/mp4box/builds/build6/src/filters/mux_isom.c:5863:6
    #2 0xd6ab36 in mp4_mux_process /programs/mp4box/builds/build6/src/filters/mux_isom.c:6033:3
    #3 0xb7c2ae in gf_filter_process_task /programs/mp4box/builds/build6/src/filter_core/filter.c:2515:7
    #4 0xb5d7eb in gf_fs_thread_proc /programs/mp4box/builds/build6/src/filter_core/filter_session.c:1756:3
    #5 0xb5c694 in gf_fs_run /programs/mp4box/builds/build6/src/filter_core/filter_session.c:2000:2
    #6 0x910850 in gf_media_fragment_file /programs/mp4box/builds/build6/src/media_tools/isom_tools.c:3816:6
    #7 0x4e6fcc in mp4boxMain /programs/mp4box/builds/build6/applications/mp4box/main.c:6455:7
    #8 0x7ff7959040b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #9 0x41ea6d in _start (/programs/mp4box/builds/build6/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /programs/mp4box/builds/build6/src/filters/mux_isom.c:3582:184 in mp4_mux_cenc_update
==15641==ABORTING
/collect/collec.sh: line 18: 15641 Aborted(core dumped)
------------------------
```
--- end body ---
