## 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-rev1727-g8be34973d-master
```

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

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

## Pocs

[poc.zip](https://github.com/gpac/gpac/files/8020714/poc.zip)


## Crash output
```
==21814==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000014 (pc 0x00000089c556 bp 0x7ffeb0b93590 sp 0x7ffeb0b932a0 T0)
==21814==The signal is caused by a READ memory access.
==21814==Hint: address points to the zero page.
    #0 0x89c556 in MergeTrack/programs/mp4box/builds/build10/src/isomedia/track.c:833:7
    #1 0x7c70d3 in MergeFragment/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:92:7
    #2 0x7cb174 in gf_isom_parse_movie_boxes_internal/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:681:9
    #3 0x7cb174 in gf_isom_parse_movie_boxes/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:812:6
    #4 0x7ccca6 in gf_isom_open_file/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:932:19
    #5 0x4e14c6 in mp4boxMain/programs/mp4box/builds/build10/applications/mp4box/main.c:5984:12
    #6 0x7f97cc63c0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #7 0x41ea6d in _start (/zhengjie/cmdline-fuzz/programs/mp4box/builds/build10/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV/programs/mp4box/builds/build10/src/isomedia/track.c:833:7 in MergeTrack
==21814==ABORTING
```
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-rev1727-g8be34973d-master
```

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

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

## Pocs

[poc.zip](https://github.com/gpac/gpac/files/8020714/poc.zip)


## Crash output
```
==21814==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000014 (pc 0x00000089c556 bp 0x7ffeb0b93590 sp 0x7ffeb0b932a0 T0)
==21814==The signal is caused by a READ memory access.
==21814==Hint: address points to the zero page.
    #0 0x89c556 in MergeTrack/programs/mp4box/builds/build10/src/isomedia/track.c:833:7
    #1 0x7c70d3 in MergeFragment/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:92:7
    #2 0x7cb174 in gf_isom_parse_movie_boxes_internal/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:681:9
    #3 0x7cb174 in gf_isom_parse_movie_boxes/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:812:6
    #4 0x7ccca6 in gf_isom_open_file/programs/mp4box/builds/build10/src/isomedia/isom_intern.c:932:19
    #5 0x4e14c6 in mp4boxMain/programs/mp4box/builds/build10/applications/mp4box/main.c:5984:12
    #6 0x7f97cc63c0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #7 0x41ea6d in _start (/zhengjie/cmdline-fuzz/programs/mp4box/builds/build10/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV/programs/mp4box/builds/build10/src/isomedia/track.c:833:7 in MergeTrack
==21814==ABORTING
```
--- end body ---
