libavcodec/mpegvideo.c:1694: error: Null Dereference
  pointer `desc` last assigned on line 1693 could be null and is dereferenced at line 1694, column 21.

libavcodec/mpegvideo.c:1679:1: start of procedure ff_MPV_frame_end()
1677. /* generic function for encode/decode called after a
1678.  * frame has been coded/decoded. */
1679. void ff_MPV_frame_end(MpegEncContext *s)
      ^
1680. {
1681.     int i;

libavcodec/mpegvideo.c:1684:9: Taking false branch
1682.     /* redraw edges for the frame if decoding didn't complete */
1683.     // just to make sure that all data is rendered.
1684.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
              ^
1685.         ff_xvmc_field_end(s);
1686.    } else if ((s->er.error_count || s->encoding) &&

libavcodec/mpegvideo.c:1686:16: Taking false branch
1684.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
1685.         ff_xvmc_field_end(s);
1686.    } else if ((s->er.error_count || s->encoding) &&
                     ^
1687.               !s->avctx->hwaccel &&
1688.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&

libavcodec/mpegvideo.c:1686:37: Taking true branch
1684.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
1685.         ff_xvmc_field_end(s);
1686.    } else if ((s->er.error_count || s->encoding) &&
                                          ^
1687.               !s->avctx->hwaccel &&
1688.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&

libavcodec/mpegvideo.c:1687:16: Taking true branch
1685.         ff_xvmc_field_end(s);
1686.    } else if ((s->er.error_count || s->encoding) &&
1687.               !s->avctx->hwaccel &&
                     ^
1688.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
1689.               s->unrestricted_mv &&

libavcodec/mpegvideo.c:1688:17: Taking true branch
1686.    } else if ((s->er.error_count || s->encoding) &&
1687.               !s->avctx->hwaccel &&
1688.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
                      ^
1689.               s->unrestricted_mv &&
1690.               s->current_picture.reference &&

libavcodec/mpegvideo.c:1689:15: Taking true branch
1687.               !s->avctx->hwaccel &&
1688.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
1689.               s->unrestricted_mv &&
                    ^
1690.               s->current_picture.reference &&
1691.               !s->intra_only &&

libavcodec/mpegvideo.c:1690:15: Taking true branch
1688.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
1689.               s->unrestricted_mv &&
1690.               s->current_picture.reference &&
                    ^
1691.               !s->intra_only &&
1692.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {

libavcodec/mpegvideo.c:1691:16: Taking true branch
1689.               s->unrestricted_mv &&
1690.               s->current_picture.reference &&
1691.               !s->intra_only &&
                     ^
1692.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1693.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);

libavcodec/mpegvideo.c:1692:17: Taking true branch
1690.               s->current_picture.reference &&
1691.               !s->intra_only &&
1692.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
                      ^
1693.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1694.        int hshift = desc->log2_chroma_w;

libavcodec/mpegvideo.c:1693:8: 
1691.               !s->intra_only &&
1692.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1693.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
             ^
1694.        int hshift = desc->log2_chroma_w;
1695.        int vshift = desc->log2_chroma_h;

libavutil/pixdesc.c:1464:1: start of procedure av_pix_fmt_desc_get()
  1462. }
  1463. 
  1464. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1466:9: Taking false branch
  1464. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1467.         return NULL;
  1468.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1466:24: Taking true branch
  1464. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1467.         return NULL;
  1468.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1467:9: 
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1467.         return NULL;
                ^
  1468.     return &av_pix_fmt_descriptors[pix_fmt];
  1469. }

libavutil/pixdesc.c:1469:1: return from a call to av_pix_fmt_desc_get
  1467.         return NULL;
  1468.     return &av_pix_fmt_descriptors[pix_fmt];
  1469. }
        ^
  1470. 
  1471. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavcodec/mpegvideo.c:1694:8: 
1692.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1693.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1694.        int hshift = desc->log2_chroma_w;
             ^
1695.        int vshift = desc->log2_chroma_h;
1696.        s->dsp.draw_edges(s->current_picture.f.data[0], s->linesize,
