void ff_mpv_common_defaults(MpegEncContext *s)
{
    s->y_dc_scale_table      =
    s->c_dc_scale_table      = ff_mpeg1_dc_scale_table;
    s->chroma_qscale_table   = ff_default_chroma_qscale_table;
    s->progressive_frame     = 1;
    s->progressive_sequence  = 1;
    s->picture_structure     = PICT_FRAME;

    s->coded_picture_number  = 0;
    s->picture_number        = 0;

    s->f_code                = 1;
    s->b_code                = 1;

    s->slice_context_count   = 1;
}

The product dereferences a pointer that it expects to be valid but is NULL.