Pass in pkt as a PktRef to Refs.Add()

Author: carlosmn

LibGit2Sharp/GitTransport.cs

@@ -44,7 +44,7 @@ public void Connect()
                     break;
 
                 if (pkt is PktRef)
-                    Refs.Add(pkt);
+                    Refs.Add(pkt as PktRef);
             }
         }