[oss-fuzz 6446003193708544] assert on bogus chroma definition

Ref.:

• https://oss-fuzz.com/testcase-detail/6446003193708544

vlc-demux-dec-libfuzzer: misc/picture.c:184: int picture_Setup(picture_t *, const video_format_t *restrict): Assertion `w->den >= w->num' failed.
==403== ERROR: libFuzzer: deadly signal
    #0 0x5805d754b8e1 in __sanitizer_print_stack_trace /src/llvm-project/compiler-rt/lib/asan/asan_stack.cpp:87:3
    #1 0x5805d743d688 in fuzzer::PrintStackTrace() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerUtil.cpp:210:5
    #2 0x5805d74201d5 in fuzzer::Fuzzer::CrashCallback() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:231:3
    #3 0x7ff5175d941f in libpthread.so.0
    #4 0x7ff51727e00a in __libc_signal_restore_set /build/glibc-LcI20x/glibc-2.31/sysdeps/unix/sysv/linux/internal-signals.h:86:3
    #5 0x7ff51727e00a in raise /build/glibc-LcI20x/glibc-2.31/sysdeps/unix/sysv/linux/raise.c:48:3
    #6 0x7ff51725d858 in abort /build/glibc-LcI20x/glibc-2.31/stdlib/abort.c:79:7
    #7 0x7ff51725d728 in __assert_fail_base /build/glibc-LcI20x/glibc-2.31/assert/assert.c:92:3
    #8 0x7ff51726efd5 in __assert_fail /build/glibc-LcI20x/glibc-2.31/assert/assert.c:101:3
    #9 0x5805d7b27325 in picture_Setup /src/vlc/src/misc/picture.c:184:9
    #10 0x5805d7b27f66 in picture_InitPrivate /src/vlc/src/misc/picture.c:216:9
    #11 0x5805d7b27f66 in picture_NewFromFormat /src/vlc/src/misc/picture.c:289:10
    #12 0x5805d796d2ef in DecodeFrame /src/vlc/modules/codec/rawvideo.c:251:17
    #13 0x5805d7586eb0 in test_decoder_process /src/vlc/test/src/input/decoder.c:253:23
    #14 0x5805d7585353 in EsOutSend /src/vlc/test/src/input/demux-run.c:115:9
    #15 0x5805d76a3bb3 in es_out_Send /src/vlc/include/vlc_es_out.h:157:12
    #16 0x5805d76a3bb3 in Demux /src/vlc/modules/demux/nsv.c:289:17
    #17 0x5805d7584455 in demux_process_stream /src/vlc/test/src/input/demux-run.c:312:19
    #18 0x5805d75840ef in LLVMFuzzerTestOneInput /src/vlc/test/vlc-demux-libfuzzer.c:63:5
    #19 0x5805d74218bd in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:619:13
    #20 0x5805d740c632 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:329:6
    #21 0x5805d7412500 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:865:9
    #22 0x5805d743e032 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
    #23 0x7ff51725f082 in __libc_start_main /build/glibc-LcI20x/glibc-2.31/csu/libc-start.c:308:16
    #24 0x5805d740571d in _start

Samples:

• clusterfuzz-testcase-vlc-demux-dec-libfuzzer-6446003193708544