y4minput.c : removed malloc of 0 bytes to resolve warning

Change-Id: Ic143455b0880e639959732e178cd62140a510b79
diff --git a/y4minput.c b/y4minput.c
index e66fad1..bcc742a 100644
--- a/y4minput.c
+++ b/y4minput.c
@@ -978,7 +978,9 @@
     _y4m->dst_buf = (unsigned char *)malloc(_y4m->dst_buf_sz);
   else
     _y4m->dst_buf = (unsigned char *)malloc(2 * _y4m->dst_buf_sz);
-  _y4m->aux_buf = (unsigned char *)malloc(_y4m->aux_buf_sz);
+
+  if (_y4m->aux_buf_sz > 0)
+    _y4m->aux_buf = (unsigned char *)malloc(_y4m->aux_buf_sz);
   return 0;
 }