fixed notifyUserDrawing exception

src/GUI/ChatScreen.java

@@ -50,6 +50,7 @@ public class ChatScreen {
     public ChatScreen(Client client)
     {
         this.client = client;
+        activeDrawingUserBox = new JTextArea();
         yourNameDisplay.setText(client.getUserName());
         exitThisRoomButton.addActionListener(actionListener);
         sendButton.addActionListener(actionListener);