libavfilter/avfilter.c:301: error: Null Dereference
  pointer `ret` last assigned on line 296 could be null and is dereferenced by call to `ff_dlog_ref()` at line 301, column 106.

libavfilter/avfilter.c:284:1: start of procedure avfilter_get_video_buffer()
282. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)
283. 
284. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
     ^
285. {
286.     AVFilterBufferRef *ret = NULL;

libavfilter/avfilter.c:286:5: 
284. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
285. {
286.     AVFilterBufferRef *ret = NULL;
         ^
287. 
288.     av_unused char buf[16];

libavfilter/avfilter.c:289:47: 
287. 
288.     av_unused char buf[16];
289.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0);
                                                   ^
290.     av_dlog(NULL, " perms:%s w:%d h:%d\n", ff_get_ref_perms_string(buf, sizeof(buf), perms), w, h);
291. 

libavfilter/avfilter.c:258:1: start of procedure ff_dlog_link()
  256. }
  257. 
  258. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
       ^
  259. {
  260.     if (link->type == AVMEDIA_TYPE_VIDEO) {

libavfilter/avfilter.c:260:9: Taking false branch
  258. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  259. {
  260.     if (link->type == AVMEDIA_TYPE_VIDEO) {
               ^
  261.         av_dlog(ctx,
  262.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:270:9: Skipping av_get_channel_layout_string(): empty list of specs
  268.     } else {
  269.         char buf[128];
  270.         av_get_channel_layout_string(buf, sizeof(buf), -1, link->channel_layout);
               ^
  271. 
  272.         av_dlog(ctx,

libavfilter/avfilter.c:260:5: 
  258. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  259. {
  260.     if (link->type == AVMEDIA_TYPE_VIDEO) {
           ^
  261.         av_dlog(ctx,
  262.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:280:1: return from a call to ff_dlog_link
  278.                 end ? "\n" : "");
  279.     }
  280. }
       ^
  281. 
  282. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)

libavfilter/avfilter.c:292:9: Taking true branch
290.     av_dlog(NULL, " perms:%s w:%d h:%d\n", ff_get_ref_perms_string(buf, sizeof(buf), perms), w, h);
291. 
292.     if (link->dstpad->get_video_buffer)
             ^
293.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
294. 

libavfilter/avfilter.c:293:9: Skipping __function_pointer__(): unresolved function pointer
291. 
292.     if (link->dstpad->get_video_buffer)
293.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
             ^
294. 
295.     if (!ret)

libavfilter/avfilter.c:295:10: Taking true branch
293.         ret = link->dstpad->get_video_buffer(link, perms, w, h);
294. 
295.     if (!ret)
              ^
296.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
297. 

libavfilter/avfilter.c:296:9: Skipping avfilter_default_get_video_buffer(): empty list of specs
294. 
295.     if (!ret)
296.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
             ^
297. 
298.     if (ret)

libavfilter/avfilter.c:298:9: Taking false branch
296.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
297. 
298.     if (ret)
             ^
299.         ret->type = AVMEDIA_TYPE_VIDEO;
300. 

libavfilter/avfilter.c:301:47: 
299.         ret->type = AVMEDIA_TYPE_VIDEO;
300. 
301.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0); av_dlog(NULL, " returning "); ff_dlog_ref(NULL, ret, 1);
                                                   ^
302. 
303.     return ret;

libavfilter/avfilter.c:258:1: start of procedure ff_dlog_link()
  256. }
  257. 
  258. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
       ^
  259. {
  260.     if (link->type == AVMEDIA_TYPE_VIDEO) {

libavfilter/avfilter.c:260:9: Taking false branch
  258. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  259. {
  260.     if (link->type == AVMEDIA_TYPE_VIDEO) {
               ^
  261.         av_dlog(ctx,
  262.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:270:9: Skipping av_get_channel_layout_string(): empty list of specs
  268.     } else {
  269.         char buf[128];
  270.         av_get_channel_layout_string(buf, sizeof(buf), -1, link->channel_layout);
               ^
  271. 
  272.         av_dlog(ctx,

libavfilter/avfilter.c:260:5: 
  258. static void ff_dlog_link(void *ctx, AVFilterLink *link, int end)
  259. {
  260.     if (link->type == AVMEDIA_TYPE_VIDEO) {
           ^
  261.         av_dlog(ctx,
  262.                 "link[%p s:%dx%d fmt:%-16s %-16s->%-16s]%s",

libavfilter/avfilter.c:280:1: return from a call to ff_dlog_link
  278.                 end ? "\n" : "");
  279.     }
  280. }
       ^
  281. 
  282. #define FF_DPRINTF_START(ctx, func) av_dlog(NULL, "%-16s: ", #func)

libavfilter/avfilter.c:301:106: 
299.         ret->type = AVMEDIA_TYPE_VIDEO;
300. 
301.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dlog_link(NULL, link, 0); av_dlog(NULL, " returning "); ff_dlog_ref(NULL, ret, 1);
                                                                                                              ^
302. 
303.     return ret;

libavfilter/avfilter.c:230:1: start of procedure ff_dlog_ref()
  228. }
  229. 
  230. static void ff_dlog_ref(void *ctx, AVFilterBufferRef *ref, int end)
       ^
  231. {
  232.     av_unused char buf[16];

libavfilter/avfilter.c:239:9: Taking false branch
  237.             ref->pts, ref->pos);
  238. 
  239.     if (ref->video) {
               ^
  240.         av_dlog(ctx, " a:%d/%d s:%dx%d i:%c",
  241.                 ref->video->pixel_aspect.num, ref->video->pixel_aspect.den,
