Defer null pointer check to Packet class.

src/internet/model/pending-data.cc

@@ -103,14 +103,7 @@ void PendingData::Clear ()
 void PendingData::Add (uint32_t s, const uint8_t* d)
 {
   NS_LOG_FUNCTION (this << s);
-  if (d != 0)
-    {
-      data.push_back (Create<Packet> (d,s));
-    }
-  else
-    {
-      data.push_back (Create<Packet> (s));
-    }
+  data.push_back (Create<Packet> (d,s));
   size += s;
 }