libavfilter/avfilter.c:247: error: Null Dereference
  pointer `ret` last assigned on line 242 could be null and is dereferenced by call to `ff_dprintf_ref()` at line 247, column 109.

libavfilter/avfilter.c:232:1: start of procedure avfilter_get_video_buffer()
230. }
231. 
232. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
     ^
233. {
234.     AVFilterBufferRef *ret = NULL;

libavfilter/avfilter.c:234:5: 
232. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)
233. {
234.     AVFilterBufferRef *ret = NULL;
         ^
235. 
236.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dprintf_link(NULL, link, 0); dprintf(NULL, " perms:%d w:%d h:%d\n", perms, w, h);

libavfilter/avfilter.c:236:47: 
234.     AVFilterBufferRef *ret = NULL;
235. 
236.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dprintf_link(NULL, link, 0); dprintf(NULL, " perms:%d w:%d h:%d\n", perms, w, h);
                                                   ^
237. 
238.     if (link_dpad(link).get_video_buffer)

libavfilter/avfilter.c:221:1: start of procedure ff_dprintf_link()
  219. }
  220. 
  221. void ff_dprintf_link(void *ctx, AVFilterLink *link, int end)
       ^
  222. {
  223.     dprintf(ctx,

libavfilter/avfilter.c:230:1: return from a call to ff_dprintf_link
  228.             link->dst ? link->dst->filter->name : "",
  229.             end ? "\n" : "");
  230. }
       ^
  231. 
  232. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)

libavfilter/avfilter.c:238:9: Taking true branch
236.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dprintf_link(NULL, link, 0); dprintf(NULL, " perms:%d w:%d h:%d\n", perms, w, h);
237. 
238.     if (link_dpad(link).get_video_buffer)
             ^
239.         ret = link_dpad(link).get_video_buffer(link, perms, w, h);
240. 

libavfilter/avfilter.c:239:9: Skipping __function_pointer__(): unresolved function pointer
237. 
238.     if (link_dpad(link).get_video_buffer)
239.         ret = link_dpad(link).get_video_buffer(link, perms, w, h);
             ^
240. 
241.     if (!ret)

libavfilter/avfilter.c:241:10: Taking true branch
239.         ret = link_dpad(link).get_video_buffer(link, perms, w, h);
240. 
241.     if (!ret)
              ^
242.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
243. 

libavfilter/avfilter.c:242:9: Skipping avfilter_default_get_video_buffer(): empty list of specs
240. 
241.     if (!ret)
242.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
             ^
243. 
244.     if (ret)

libavfilter/avfilter.c:244:9: Taking false branch
242.         ret = avfilter_default_get_video_buffer(link, perms, w, h);
243. 
244.     if (ret)
             ^
245.         ret->type = AVMEDIA_TYPE_VIDEO;
246. 

libavfilter/avfilter.c:247:47: 
245.         ret->type = AVMEDIA_TYPE_VIDEO;
246. 
247.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dprintf_link(NULL, link, 0); dprintf(NULL, " returning "); ff_dprintf_ref(NULL, ret, 1);
                                                   ^
248. 
249.     return ret;

libavfilter/avfilter.c:221:1: start of procedure ff_dprintf_link()
  219. }
  220. 
  221. void ff_dprintf_link(void *ctx, AVFilterLink *link, int end)
       ^
  222. {
  223.     dprintf(ctx,

libavfilter/avfilter.c:230:1: return from a call to ff_dprintf_link
  228.             link->dst ? link->dst->filter->name : "",
  229.             end ? "\n" : "");
  230. }
       ^
  231. 
  232. AVFilterBufferRef *avfilter_get_video_buffer(AVFilterLink *link, int perms, int w, int h)

libavfilter/avfilter.c:247:109: 
245.         ret->type = AVMEDIA_TYPE_VIDEO;
246. 
247.     FF_DPRINTF_START(NULL, get_video_buffer); ff_dprintf_link(NULL, link, 0); dprintf(NULL, " returning "); ff_dprintf_ref(NULL, ret, 1);
                                                                                                                 ^
248. 
249.     return ret;

libavfilter/avfilter.c:194:1: start of procedure ff_dprintf_ref()
  192. }
  193. 
  194. void ff_dprintf_ref(void *ctx, AVFilterBufferRef *ref, int end)
       ^
  195. {
  196.     dprintf(ctx,

libavfilter/avfilter.c:202:9: Taking false branch
  200.             ref->pts, ref->pos);
  201. 
  202.     if (ref->video) {
               ^
  203.         dprintf(ctx, " a:%d/%d s:%dx%d i:%c",
  204.                 ref->video->pixel_aspect.num, ref->video->pixel_aspect.den,
