avcodec/h264: Clear delayed_pic on deallocation

Fixes use of freed memory

Fixes: case5_av_frame_copy_props.mp4
Found-by: Michal Zalewski <lcamtuf@coredump.cx>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
av_cold void ff_h264_free_context(H264Context *h)
{
    int i;

    ff_h264_free_tables(h, 1); // FIXME cleanup init stuff perhaps

    for (i = 0; i < MAX_SPS_COUNT; i++)
        av_freep(h->sps_buffers + i);

    for (i = 0; i < MAX_PPS_COUNT; i++)
        av_freep(h->pps_buffers + i);
}

av_cold void ff_h264_free_context(H264Context *h)
{
    int i;

    ff_h264_free_tables(h, 1); // FIXME cleanup init stuff perhaps

    for (i = 0; i < MAX_SPS_COUNT; i++)
        av_freep(h->sps_buffers + i);

    for (i = 0; i < MAX_PPS_COUNT; i++)
        av_freep(h->pps_buffers + i);
}
