Bento4 v1.6.0-640 was discovered to contain a NULL pointer dereference via the AP4_StszAtom::GetSampleSize() function.
On master compiled on 2017-09-10 (but please confirm if this affects current stable):

```
# mp4compact $FILE out.mp4
ASAN:DEADLYSIGNAL
=================================================================
==156195==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x00000060a4b3 bp 0x7ffed6dd9e30 sp 0x7ffed6dd9e30 T0)
==156195==The signal is caused by a READ memory access.
==156195==Hint: address points to the zero page.
    #0 0x60a4b2 in AP4_StszAtom::GetSampleSize(unsigned int, unsigned int&) /tmp/Bento4-master-2017-09-10/Source/C++/Core/Ap4StszAtom.cpp:150:27
    #1 0x5421ec in AP4_CompactingProcessor::TrackHandler::ProcessTrack() /tmp/Bento4-master-2017-09-10/Source/C++/Apps/Mp4Compact/Mp4Compact.cpp:132:15
    #2 0x5bef58 in AP4_Processor::Process(AP4_ByteStream&, AP4_ByteStream&, AP4_ByteStream*, AP4_Processor::ProgressListener*, AP4_AtomFactory&) /tmp/Bento4-master-2017-09-10/Source/C++/Core/Ap4Processor.cpp:617:35
    #3 0x542f69 in main /tmp/Bento4-master-2017-09-10/Source/C++/Apps/Mp4Compact/Mp4Compact.cpp:220:25
    #4 0x7f96ff492680 in __libc_start_main /var/tmp/portage/sys-libs/glibc-2.23-r4/work/glibc-2.23/csu/../csu/libc-start.c:289
    #5 0x44ec88 in _start (/usr/bin/mp4compact+0x44ec88)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/Bento4-master-2017-09-10/Source/C++/Core/Ap4StszAtom.cpp:150:27 in AP4_StszAtom::GetSampleSize(unsigned int, unsigned int&)
==156195==ABORTING
```

Testcase:
https://github.com/asarubbo/poc/blob/master/00363-bento4-NULLptr-AP4_StszAtom_GetSampleSize
NULL pointer dereference in AP4_StszAtom::GetSampleSize (Ap4StszAtom.cpp)
This is a GitHub Issue
repo:Bento4
owner:axiomatic-systems
Title : NULL pointer dereference in AP4_StszAtom::GetSampleSize (Ap4StszAtom.cpp)
Issue date:

--- start body ---
On master compiled on 2017-09-10 (but please confirm if this affects current stable):

```
# mp4compact $FILE out.mp4
ASAN:DEADLYSIGNAL
=================================================================
==156195==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x00000060a4b3 bp 0x7ffed6dd9e30 sp 0x7ffed6dd9e30 T0)
==156195==The signal is caused by a READ memory access.
==156195==Hint: address points to the zero page.
    #0 0x60a4b2 in AP4_StszAtom::GetSampleSize(unsigned int, unsigned int&) /tmp/Bento4-master-2017-09-10/Source/C++/Core/Ap4StszAtom.cpp:150:27
    #1 0x5421ec in AP4_CompactingProcessor::TrackHandler::ProcessTrack() /tmp/Bento4-master-2017-09-10/Source/C++/Apps/Mp4Compact/Mp4Compact.cpp:132:15
    #2 0x5bef58 in AP4_Processor::Process(AP4_ByteStream&, AP4_ByteStream&, AP4_ByteStream*, AP4_Processor::ProgressListener*, AP4_AtomFactory&) /tmp/Bento4-master-2017-09-10/Source/C++/Core/Ap4Processor.cpp:617:35
    #3 0x542f69 in main /tmp/Bento4-master-2017-09-10/Source/C++/Apps/Mp4Compact/Mp4Compact.cpp:220:25
    #4 0x7f96ff492680 in __libc_start_main /var/tmp/portage/sys-libs/glibc-2.23-r4/work/glibc-2.23/csu/../csu/libc-start.c:289
    #5 0x44ec88 in _start (/usr/bin/mp4compact+0x44ec88)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/Bento4-master-2017-09-10/Source/C++/Core/Ap4StszAtom.cpp:150:27 in AP4_StszAtom::GetSampleSize(unsigned int, unsigned int&)
==156195==ABORTING
```

Testcase:
https://github.com/asarubbo/poc/blob/master/00363-bento4-NULLptr-AP4_StszAtom_GetSampleSize
--- end body ---
