libavcodec/vp3.c:1856: error: Null Dereference
  pointer `&gb->buffer` last assigned on line 1854 could be null and is dereferenced by call to `get_bits1()` at line 1856, column 22.

libavcodec/vp3.c:1844:1: start of procedure vp3_decode_frame()
1842. }
1843. 
1844. static int vp3_decode_frame(AVCodecContext *avctx,
      ^
1845.                             void *data, int *data_size,
1846.                             AVPacket *avpkt)

libavcodec/vp3.c:1848:5: 
1846.                             AVPacket *avpkt)
1847. {
1848.     const uint8_t *buf = avpkt->data;
          ^
1849.     int buf_size = avpkt->size;
1850.     Vp3DecodeContext *s = avctx->priv_data;

libavcodec/vp3.c:1849:5: 
1847. {
1848.     const uint8_t *buf = avpkt->data;
1849.     int buf_size = avpkt->size;
          ^
1850.     Vp3DecodeContext *s = avctx->priv_data;
1851.     GetBitContext gb;

libavcodec/vp3.c:1850:5: 
1848.     const uint8_t *buf = avpkt->data;
1849.     int buf_size = avpkt->size;
1850.     Vp3DecodeContext *s = avctx->priv_data;
          ^
1851.     GetBitContext gb;
1852.     int i;

libavcodec/vp3.c:1854:5: 
1852.     int i;
1853. 
1854.     init_get_bits(&gb, buf, buf_size * 8);
          ^
1855. 
1856.     if (s->theora && get_bits1(&gb))

libavcodec/get_bits.h:343:1: start of procedure init_get_bits()
  341.  * @param bit_size the size of the buffer in bits
  342.  */
  343. static inline void init_get_bits(GetBitContext *s, const uint8_t *buffer,
       ^
  344.                                  int bit_size)
  345. {

libavcodec/get_bits.h:346:5: 
  344.                                  int bit_size)
  345. {
  346.     int buffer_size = (bit_size+7)>>3;
           ^
  347.     if (buffer_size < 0 || bit_size < 0) {
  348.         buffer_size = bit_size = 0;

libavcodec/get_bits.h:347:9: Taking true branch
  345. {
  346.     int buffer_size = (bit_size+7)>>3;
  347.     if (buffer_size < 0 || bit_size < 0) {
               ^
  348.         buffer_size = bit_size = 0;
  349.         buffer = NULL;

libavcodec/get_bits.h:348:9: 
  346.     int buffer_size = (bit_size+7)>>3;
  347.     if (buffer_size < 0 || bit_size < 0) {
  348.         buffer_size = bit_size = 0;
               ^
  349.         buffer = NULL;
  350.     }

libavcodec/get_bits.h:349:9: 
  347.     if (buffer_size < 0 || bit_size < 0) {
  348.         buffer_size = bit_size = 0;
  349.         buffer = NULL;
               ^
  350.     }
  351. 

libavcodec/get_bits.h:352:5: 
  350.     }
  351. 
  352.     s->buffer       = buffer;
           ^
  353.     s->size_in_bits = bit_size;
  354. #if !UNCHECKED_BITSTREAM_READER

libavcodec/get_bits.h:353:5: 
  351. 
  352.     s->buffer       = buffer;
  353.     s->size_in_bits = bit_size;
           ^
  354. #if !UNCHECKED_BITSTREAM_READER
  355.     s->size_in_bits_plus8 = bit_size + 8;

libavcodec/get_bits.h:355:5: 
  353.     s->size_in_bits = bit_size;
  354. #if !UNCHECKED_BITSTREAM_READER
  355.     s->size_in_bits_plus8 = bit_size + 8;
           ^
  356. #endif
  357.     s->buffer_end   = buffer + buffer_size;

libavcodec/get_bits.h:357:5: 
  355.     s->size_in_bits_plus8 = bit_size + 8;
  356. #endif
  357.     s->buffer_end   = buffer + buffer_size;
           ^
  358.     s->index        = 0;
  359. }

libavcodec/get_bits.h:358:5: 
  356. #endif
  357.     s->buffer_end   = buffer + buffer_size;
  358.     s->index        = 0;
           ^
  359. }
  360. 

libavcodec/get_bits.h:359:1: return from a call to init_get_bits
  357.     s->buffer_end   = buffer + buffer_size;
  358.     s->index        = 0;
  359. }
       ^
  360. 
  361. static inline void align_get_bits(GetBitContext *s)

libavcodec/vp3.c:1856:9: Taking true branch
1854.     init_get_bits(&gb, buf, buf_size * 8);
1855. 
1856.     if (s->theora && get_bits1(&gb))
              ^
1857.     {
1858.         av_log(avctx, AV_LOG_ERROR, "Header packet passed to frame decoder, skipping\n");

libavcodec/vp3.c:1856:22: 
1854.     init_get_bits(&gb, buf, buf_size * 8);
1855. 
1856.     if (s->theora && get_bits1(&gb))
                           ^
1857.     {
1858.         av_log(avctx, AV_LOG_ERROR, "Header packet passed to frame decoder, skipping\n");

libavcodec/get_bits.h:259:1: start of procedure get_bits1()
  257. }
  258. 
  259. static inline unsigned int get_bits1(GetBitContext *s)
       ^
  260. {
  261.     unsigned int index = s->index;

libavcodec/get_bits.h:261:5: 
  259. static inline unsigned int get_bits1(GetBitContext *s)
  260. {
  261.     unsigned int index = s->index;
           ^
  262.     uint8_t result = s->buffer[index>>3];
  263. #ifdef ALT_BITSTREAM_READER_LE

libavcodec/get_bits.h:262:5: 
  260. {
  261.     unsigned int index = s->index;
  262.     uint8_t result = s->buffer[index>>3];
           ^
  263. #ifdef ALT_BITSTREAM_READER_LE
  264.     result >>= index & 7;
