libavfilter/defaults.c:101: error: Integer Overflow L2
  ([0, +oo] - 1):unsigned32 by call to `avfilter_unref_buffer`.

libavfilter/defaults.c:101:5: Call
 99.         out = link->dst->outputs[0];
100. 
101.     avfilter_unref_buffer(link->cur_buf);
         ^
102.     link->cur_buf = NULL;
103. 

libavfilter/avfilter.c:61:1: <LHS trace>
59. }
60. 
61. void avfilter_unref_buffer(AVFilterBufferRef *ref)
    ^
62. {
63.     if(!(--ref->buf->refcount))

libavfilter/avfilter.c:61:1: Parameter `ref->buf->refcount`
  59. }
  60. 
  61. void avfilter_unref_buffer(AVFilterBufferRef *ref)
      ^
  62. {
  63.     if(!(--ref->buf->refcount))

libavfilter/avfilter.c:63:10: Binary operation: ([0, +oo] - 1):unsigned32 by call to `avfilter_unref_buffer` 
  61. void avfilter_unref_buffer(AVFilterBufferRef *ref)
  62. {
  63.     if(!(--ref->buf->refcount))
               ^
  64.         ref->buf->free(ref->buf);
  65.     av_free(ref->video);
