Close messaging window if the connection is broken

src/main/java/ChatClient.java

@@ -60,6 +60,7 @@ public class ChatClient extends JFrame implements KeyListener {
             }
         } catch (IOException e) {
             JOptionPane.showMessageDialog(null, "Verbindung zum Server \"" + address + "\" fehlgeschlagen.");
+            dispose();
         } finally {
             if (null != connectionToServer) {
                 try {
@@ -80,7 +81,6 @@ public class ChatClient extends JFrame implements KeyListener {
             if(null != toServerWriter) {
                 toServerWriter.close();
             }
-            
         }
     }