libavfilter/avfilter.c:295: error: Null Dereference
  pointer `ret` last assigned on line 290 could be null and is dereferenced by call to `ff_dlog_ref()` at line 295, column 106.

libavfilter/avfilter.c:278:1: start of procedure avfilter_get_video_buffer()
276. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)
277. 
278. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
     ^
279. {
280.     AVFilterBufferRef *ret = NULL;

libavfilter/avfilter.c:280:5: 
278. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
279. {
280.     AVFilterBufferRef *ret = NULL;
         ^
281. 
282.     av_unused char buf[16];

libavfilter/avfilter.c:283:47: 
281. 
282.     av_unused char buf[16];
283.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0);
                                                   ^
284.     av_dlog(NULL, " perms:%s w:%d h:%d\n", ff_get_ref_perms_string(buf, sizeof(buf), perms), w, h);
285. 

libavfilter/avfilter.c:252:1: start of procedure ff_dlog_link()
  250. }
  251. 
  252. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
       ^
  253. {
  254.     if (link->type == AVMEDIA_TYPE_VIDEO) {

libavfilter/avfilter.c:254:9: Taking false branch
  252. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  253. {
  254.     if (link->type == AVMEDIA_TYPE_VIDEO) {
               ^
  255.         av_dlog(ctx,
  256.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:264:9: Skipping av_get_channel_layout_string(): empty list of specs
  262.     } else {
  263.         char buf[128];
  264.         av_get_channel_layout_string(buf, sizeof(buf), -1, link->channel_layout);
               ^
  265. 
  266.         av_dlog(ctx,

libavfilter/avfilter.c:254:5: 
  252. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  253. {
  254.     if (link->type == AVMEDIA_TYPE_VIDEO) {
           ^
  255.         av_dlog(ctx,
  256.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:274:1: return from a call to ff_dlog_link
  272.                 end ? "\n" : "");
  273.     }
  274. }
       ^
  275. 
  276. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)

libavfilter/avfilter.c:286:9: Taking true branch
284.     av_dlog(NULL, " perms:%s w:%d h:%d\n", ff_get_ref_perms_string(buf, sizeof(buf), perms), w, h);
285. 
286.     if (link->dstpad->get_video_buffer)
             ^
287.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
288. 

libavfilter/avfilter.c:287:9: Skipping __function_pointer__(): unresolved function pointer
285. 
286.     if (link->dstpad->get_video_buffer)
287.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
             ^
288. 
289.     if (!ret)

libavfilter/avfilter.c:289:10: Taking true branch
287.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
288. 
289.     if (!ret)
              ^
290.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
291. 

libavfilter/avfilter.c:290:9: Skipping avfilter_default_get_video_buffer(): empty list of specs
288. 
289.     if (!ret)
290.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
             ^
291. 
292.     if (ret)

libavfilter/avfilter.c:292:9: Taking false branch
290.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
291. 
292.     if (ret)
             ^
293.         ret->type = AVMEDIA_TYPE_VIDEO;
294. 

libavfilter/avfilter.c:295:47: 
293.         ret->type = AVMEDIA_TYPE_VIDEO;
294. 
295.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0); av_dlog(NULL, " returning "); ff_dlog_ref(NULL, ret, 1);
                                                   ^
296. 
297.     return ret;

libavfilter/avfilter.c:252:1: start of procedure ff_dlog_link()
  250. }
  251. 
  252. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
       ^
  253. {
  254.     if (link->type == AVMEDIA_TYPE_VIDEO) {

libavfilter/avfilter.c:254:9: Taking false branch
  252. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  253. {
  254.     if (link->type == AVMEDIA_TYPE_VIDEO) {
               ^
  255.         av_dlog(ctx,
  256.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:264:9: Skipping av_get_channel_layout_string(): empty list of specs
  262.     } else {
  263.         char buf[128];
  264.         av_get_channel_layout_string(buf, sizeof(buf), -1, link->channel_layout);
               ^
  265. 
  266.         av_dlog(ctx,

libavfilter/avfilter.c:254:5: 
  252. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  253. {
  254.     if (link->type == AVMEDIA_TYPE_VIDEO) {
           ^
  255.         av_dlog(ctx,
  256.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:274:1: return from a call to ff_dlog_link
  272.                 end ? "\n" : "");
  273.     }
  274. }
       ^
  275. 
  276. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)

libavfilter/avfilter.c:295:106: 
293.         ret->type = AVMEDIA_TYPE_VIDEO;
294. 
295.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0); av_dlog(NULL, " returning "); ff_dlog_ref(NULL, ret, 1);
                                                                                                              ^
296. 
297.     return ret;

libavfilter/avfilter.c:224:1: start of procedure ff_dlog_ref()
  222. }
  223. 
  224. static void ff_dlog_ref(void *ctx, AVFilterBufferRef *ref, int end)
       ^
  225. {
  226.     av_unused char buf[16];

libavfilter/avfilter.c:233:9: Taking false branch
  231.             ref->pts, ref->pos);
  232. 
  233.     if (ref->video) {
               ^
  234.         av_dlog(ctx, " a:%d/%d s:%dx%d i:%c",
  235.                 ref->video->pixel_aspect.num, ref->video->pixel_aspect.den,
