libavformat/matroskaenc.c:312: error: Null Dereference
  pointer `seekhead->entries` last assigned on line 306 could be null and is dereferenced at line 312, column 5.

libavformat/matroskaenc.c:298:1: start of procedure mkv_add_seekhead_entry()
296. }
297. 
298. static int mkv_add_seekhead_entry(mkv_seekhead *seekhead, unsigned int elementid, uint64_t filepos)
     ^
299. {
300.     int err;

libavformat/matroskaenc.c:303:9: Taking true branch
301. 
302.     // don't store more elements than we reserved space for
303.     if (seekhead->max_entries > 0 && seekhead->max_entries <= seekhead->num_entries)
             ^
304.         return -1;
305. 

libavformat/matroskaenc.c:303:38: Taking false branch
301. 
302.     // don't store more elements than we reserved space for
303.     if (seekhead->max_entries > 0 && seekhead->max_entries <= seekhead->num_entries)
                                          ^
304.         return -1;
305. 

libavformat/matroskaenc.c:306:9: 
304.         return -1;
305. 
306.     if ((err = av_reallocp_array(&seekhead->entries, seekhead->num_entries + 1,
             ^
307.                                  sizeof(*seekhead->entries))) < 0) {
308.         seekhead->num_entries = 0;

libavutil/mem.c:167:1: start of procedure av_reallocp_array()
  165. }
  166. 
  167. int av_reallocp_array(void *ptr, size_t nmemb, size_t size)
       ^
  168. {
  169.     void **ptrptr = ptr;

libavutil/mem.c:169:5: 
  167. int av_reallocp_array(void *ptr, size_t nmemb, size_t size)
  168. {
  169.     void **ptrptr = ptr;
           ^
  170.     void *ret;
  171.     if (!size || nmemb >= INT_MAX / size)

libavutil/mem.c:171:10: Taking false branch
  169.     void **ptrptr = ptr;
  170.     void *ret;
  171.     if (!size || nmemb >= INT_MAX / size)
                ^
  172.         return AVERROR(ENOMEM);
  173.     if (!nmemb) {

libavutil/mem.c:171:18: Taking false branch
  169.     void **ptrptr = ptr;
  170.     void *ret;
  171.     if (!size || nmemb >= INT_MAX / size)
                        ^
  172.         return AVERROR(ENOMEM);
  173.     if (!nmemb) {

libavutil/mem.c:173:10: Taking true branch
  171.     if (!size || nmemb >= INT_MAX / size)
  172.         return AVERROR(ENOMEM);
  173.     if (!nmemb) {
                ^
  174.         av_freep(ptr);
  175.         return 0;

libavutil/mem.c:174:9: 
  172.         return AVERROR(ENOMEM);
  173.     if (!nmemb) {
  174.         av_freep(ptr);
               ^
  175.         return 0;
  176.     }

libavutil/mem.c:198:1: start of procedure av_freep()
    196. }
    197. 
    198. void av_freep(void *arg)
         ^
    199. {
    200.     void **ptr = (void **)arg;

libavutil/mem.c:200:5: 
    198. void av_freep(void *arg)
    199. {
    200.     void **ptr = (void **)arg;
             ^
    201.     av_free(*ptr);
    202.     *ptr = NULL;

libavutil/mem.c:201:5: 
    199. {
    200.     void **ptr = (void **)arg;
    201.     av_free(*ptr);
             ^
    202.     *ptr = NULL;
    203. }

libavutil/mem.c:186:1: start of procedure av_free()
      184. }
      185. 
      186. void av_free(void *ptr)
           ^
      187. {
      188. #if CONFIG_MEMALIGN_HACK

libavutil/mem.c:194:5: 
      192.     _aligned_free(ptr);
      193. #else
      194.     free(ptr);
               ^
      195. #endif
      196. }

libavutil/mem.c:196:1: return from a call to av_free
      194.     free(ptr);
      195. #endif
      196. }
           ^
      197. 
      198. void av_freep(void *arg)

libavutil/mem.c:202:5: 
    200.     void **ptr = (void **)arg;
    201.     av_free(*ptr);
    202.     *ptr = NULL;
             ^
    203. }
    204. 

libavutil/mem.c:203:1: return from a call to av_freep
    201.     av_free(*ptr);
    202.     *ptr = NULL;
    203. }
         ^
    204. 
    205. void *av_mallocz(size_t size)

libavutil/mem.c:175:9: 
  173.     if (!nmemb) {
  174.         av_freep(ptr);
  175.         return 0;
               ^
  176.     }
  177.     ret = av_realloc(*ptrptr, nmemb * size);

libavutil/mem.c:184:1: return from a call to av_reallocp_array
  182.     *ptrptr = ret;
  183.     return 0;
  184. }
       ^
  185. 
  186. void av_free(void *ptr)

libavformat/matroskaenc.c:306:9: Taking false branch
304.         return -1;
305. 
306.     if ((err = av_reallocp_array(&seekhead->entries, seekhead->num_entries + 1,
             ^
307.                                  sizeof(*seekhead->entries))) < 0) {
308.         seekhead->num_entries = 0;

libavformat/matroskaenc.c:312:5: 
310.     }
311. 
312.     seekhead->entries[seekhead->num_entries].elementid    = elementid;
         ^
313.     seekhead->entries[seekhead->num_entries++].segmentpos = filepos - seekhead->segment_offset;
314. 
