libavcodec/vp3.c:1847: error: Null Dereference
  pointer `&gb->buffer` last assigned on line 1839 could be null and is dereferenced by call to `get_bits1()` at line 1847, column 20.

libavcodec/vp3.c:1829:1: start of procedure vp3_decode_frame()
1827.  * This is the ffmpeg/libavcodec API frame decode function.
1828.  */
1829. static int vp3_decode_frame(AVCodecContext *avctx,
      ^
1830.                             void *data, int *data_size,
1831.                             AVPacket *avpkt)

libavcodec/vp3.c:1833:5: 
1831.                             AVPacket *avpkt)
1832. {
1833.     const uint8_t *buf = avpkt->data;
          ^
1834.     int buf_size = avpkt->size;
1835.     Vp3DecodeContext *s = avctx->priv_data;

libavcodec/vp3.c:1834:5: 
1832. {
1833.     const uint8_t *buf = avpkt->data;
1834.     int buf_size = avpkt->size;
          ^
1835.     Vp3DecodeContext *s = avctx->priv_data;
1836.     GetBitContext gb;

libavcodec/vp3.c:1835:5: 
1833.     const uint8_t *buf = avpkt->data;
1834.     int buf_size = avpkt->size;
1835.     Vp3DecodeContext *s = avctx->priv_data;
          ^
1836.     GetBitContext gb;
1837.     int i;

libavcodec/vp3.c:1839:5: 
1837.     int i;
1838. 
1839.     init_get_bits(&gb, buf, buf_size * 8);
          ^
1840. 
1841.     if (s->theora && get_bits1(&gb))

libavcodec/get_bits.h:391:1: start of procedure init_get_bits()
  389.  * responsible for checking for the buffer end yourself (take advantage of the padding)!
  390.  */
  391. static inline void init_get_bits(GetBitContext *s,
       ^
  392.                    const uint8_t *buffer, int bit_size)
  393. {

libavcodec/get_bits.h:394:5: 
  392.                    const uint8_t *buffer, int bit_size)
  393. {
  394.     int buffer_size = (bit_size+7)>>3;
           ^
  395.     if (buffer_size < 0 || bit_size < 0) {
  396.         buffer_size = bit_size = 0;

libavcodec/get_bits.h:395:9: Taking true branch
  393. {
  394.     int buffer_size = (bit_size+7)>>3;
  395.     if (buffer_size < 0 || bit_size < 0) {
               ^
  396.         buffer_size = bit_size = 0;
  397.         buffer = NULL;

libavcodec/get_bits.h:396:9: 
  394.     int buffer_size = (bit_size+7)>>3;
  395.     if (buffer_size < 0 || bit_size < 0) {
  396.         buffer_size = bit_size = 0;
               ^
  397.         buffer = NULL;
  398.     }

libavcodec/get_bits.h:397:9: 
  395.     if (buffer_size < 0 || bit_size < 0) {
  396.         buffer_size = bit_size = 0;
  397.         buffer = NULL;
               ^
  398.     }
  399. 

libavcodec/get_bits.h:400:5: 
  398.     }
  399. 
  400.     s->buffer       = buffer;
           ^
  401.     s->size_in_bits = bit_size;
  402.     s->buffer_end   = buffer + buffer_size;

libavcodec/get_bits.h:401:5: 
  399. 
  400.     s->buffer       = buffer;
  401.     s->size_in_bits = bit_size;
           ^
  402.     s->buffer_end   = buffer + buffer_size;
  403. #ifdef ALT_BITSTREAM_READER

libavcodec/get_bits.h:402:5: 
  400.     s->buffer       = buffer;
  401.     s->size_in_bits = bit_size;
  402.     s->buffer_end   = buffer + buffer_size;
           ^
  403. #ifdef ALT_BITSTREAM_READER
  404.     s->index        = 0;

libavcodec/get_bits.h:404:5: 
  402.     s->buffer_end   = buffer + buffer_size;
  403. #ifdef ALT_BITSTREAM_READER
  404.     s->index        = 0;
           ^
  405. #elif defined A32_BITSTREAM_READER
  406.     s->buffer_ptr   = (uint32_t*)((intptr_t)buffer & ~3);

libavcodec/get_bits.h:410:1: return from a call to init_get_bits
  408.     skip_bits_long(s, 0);
  409. #endif
  410. }
       ^
  411. 
  412. static inline void align_get_bits(GetBitContext *s)

libavcodec/vp3.c:1841:9: Taking false branch
1839.     init_get_bits(&gb, buf, buf_size * 8);
1840. 
1841.     if (s->theora && get_bits1(&gb))
              ^
1842.     {
1843.         av_log(avctx, AV_LOG_ERROR, "Header packet passed to frame decoder, skipping\n");

libavcodec/vp3.c:1847:20: 
1845.     }
1846. 
1847.     s->keyframe = !get_bits1(&gb);
                         ^
1848.     if (!s->theora)
1849.         skip_bits(&gb, 1);

libavcodec/get_bits.h:311:1: start of procedure get_bits1()
  309. }
  310. 
  311. static inline unsigned int get_bits1(GetBitContext *s){
       ^
  312. #ifdef ALT_BITSTREAM_READER
  313.     unsigned int index = s->index;

libavcodec/get_bits.h:313:5: 
  311. static inline unsigned int get_bits1(GetBitContext *s){
  312. #ifdef ALT_BITSTREAM_READER
  313.     unsigned int index = s->index;
           ^
  314.     uint8_t result = s->buffer[index>>3];
  315. #ifdef ALT_BITSTREAM_READER_LE

libavcodec/get_bits.h:314:5: 
  312. #ifdef ALT_BITSTREAM_READER
  313.     unsigned int index = s->index;
  314.     uint8_t result = s->buffer[index>>3];
           ^
  315. #ifdef ALT_BITSTREAM_READER_LE
  316.     result >>= index & 7;
