Attempt to fix double disconnects

src/main/java/net/minecraft/server/NetServerHandler.java

@@ -545,9 +545,11 @@ public class NetServerHandler extends NetHandler implements ICommandListener {
     }
 
     public void a(String s, Object[] aobject) {
+        if (!this.c) {
             a.info(this.e.name + " lost connection: " + s);
             this.d.f.a((Packet) (new Packet3Chat("\u00A7e" + this.e.name + " left the game.")));
             this.d.f.c(this.e);
+        }
         this.c = true;
     }