## 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-rev1740-gbd98129fd-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/8032697/poc.zip)


## Crash output
```
==35942==ERROR: AddressSanitizer: SEGV on unknown address 0x00000000002c (pc 0x0000007c72df bp 0x7ffd62baabf0 sp 0x7ffd62baa9e0 T0)
==35942==The signal is caused by a READ memory access.
==35942==Hint: address points to the zero page.
    #0 0x7c72df in MergeFragment /programs/mp4box/builds/build12/src/isomedia/isom_intern.c
    #1 0x7cb3c4 in gf_isom_parse_movie_boxes_internal /programs/mp4box/builds/build12/src/isomedia/isom_intern.c:681:9
    #2 0x7cb3c4 in gf_isom_parse_movie_boxes /programs/mp4box/builds/build12/src/isomedia/isom_intern.c:812:6
    #3 0x7ccef6 in gf_isom_open_file /programs/mp4box/builds/build12/src/isomedia/isom_intern.c:932:19
    #4 0x4ebd9f in dump_isom_scene_stats /programs/mp4box/builds/build12/applications/mp4box/filedump.c:378:15
    #5 0x4e0c2a in mp4boxMain /programs/mp4box/builds/build12/applications/mp4box/main.c:6152:18
    #6 0x7fc1740af0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #7 0x41ea6d in _start (/programs/mp4box/builds/build12/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /programs/mp4box/builds/build12/src/isomedia/isom_intern.c in MergeFragment
==35942==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-rev1740-gbd98129fd-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/8032697/poc.zip)


## Crash output
```
==35942==ERROR: AddressSanitizer: SEGV on unknown address 0x00000000002c (pc 0x0000007c72df bp 0x7ffd62baabf0 sp 0x7ffd62baa9e0 T0)
==35942==The signal is caused by a READ memory access.
==35942==Hint: address points to the zero page.
    #0 0x7c72df in MergeFragment /programs/mp4box/builds/build12/src/isomedia/isom_intern.c
    #1 0x7cb3c4 in gf_isom_parse_movie_boxes_internal /programs/mp4box/builds/build12/src/isomedia/isom_intern.c:681:9
    #2 0x7cb3c4 in gf_isom_parse_movie_boxes /programs/mp4box/builds/build12/src/isomedia/isom_intern.c:812:6
    #3 0x7ccef6 in gf_isom_open_file /programs/mp4box/builds/build12/src/isomedia/isom_intern.c:932:19
    #4 0x4ebd9f in dump_isom_scene_stats /programs/mp4box/builds/build12/applications/mp4box/filedump.c:378:15
    #5 0x4e0c2a in mp4boxMain /programs/mp4box/builds/build12/applications/mp4box/main.c:6152:18
    #6 0x7fc1740af0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #7 0x41ea6d in _start (/programs/mp4box/builds/build12/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /programs/mp4box/builds/build12/src/isomedia/isom_intern.c in MergeFragment
==35942==ABORTING
```
--- end body ---
