exit listener thread if BufferedReader returns null

git-svn-id: svn://anubis/gvsu@149 45c1a28c-8058-47b2-ae61-ca45b979098e

cs656/lab2/src/ChatClient.java

@@ -77,6 +77,8 @@ public class ChatClient
                     {
                         /* read and print a message from a peer */
                         String in = br.readLine();
+                        if (in == null)
+                            break;
                         System.out.println(in);
                     }
                 }