fix bugs

src/main/java/com/university/chat/Server/ClientSession.java

@@ -73,6 +73,7 @@ public class ClientSession implements Runnable {
             //  6. Otherwise, create the user's folders with FileManager.createUserFolders(...)
             //      and send back LOGIN_SUCCESS.
             this.username = requestedUser;
+            FileManager.createUserFolders(username);
             out.writeObject(new ChatMessage(MessageType.LOGIN_SUCCESS, "Server", null, "Welcome "+username));
             out.flush();
             System.out.println("User logged in: "+username);