Java GUI java.lang.NullPointerException using GridBagLayout

I am trying to design a GUI program using Java. Below is a part of my code. I get a nullExceptionPointer where i have a comment saying there is a nullExceptionPointer over here. I believe it is the new GridBagLayout() causing the problem. But above at the //panel workouts section i do the same thing and it works, as well as my other panels which i am not including. Any ideas, I am a noob and many of my code may not make sense but if anyone has any ideas on what to check it would be greatly appreciated.

Thank you in advance

//Panel Workouts

        btnCreateWPlan = new JButton("Create Workout");
        btnDeleteWPlan = new JButton("Delete Workout");
        btnModifyWPlan = new JButton("Modify Workout");
        btnBack3 = new JButton("Back");

        panelWorkout.setLayout(new GridBagLayout());
        setPosition(0,0);
        panelWorkout.add(btnCreateWPlan,gbc);
        setPosition(0,1);
        panelWorkout.add(btnDeleteWPlan,gbc);
        setPosition(0,2);
        panelWorkout.add(btnModifyWPlan,gbc);
        setPosition(0,3);
        panelWorkout.add(btnBack3,gbc);

        //Panel add client

        lblFirstname = new JLabel("Firstname: ");
        lblLastname = new JLabel("Lastname :");
        lblCustomerID = new JLabel("Customer ID: ");
        lblAge = new JLabel("Age: ");
        lblDietPlan = new JLabel("Diet Plan: ");
        lblWorkoutPlan = new JLabel("Workout Plan: ");

        txtFirstname = new JTextField(15);
        txtLastname = new JTextField(15);
        txtCustomerID = new JTextField(15);
        txtAge = new JTextField(15);
        txtDietPlan = new JTextField(15);
        txtWorkoutPlan = new JTextField(15);

        btnRegister = new JButton("Register");
        btnBack4 = new JButton("Back");

        panelAddClient.setLayout(new GridBagLayout()); // null exception over here
        setPosition(0,0);
        panelAddClient.add(lblFirstname,gbc);
        setPosition(0,1);
        panelAddClient.add(lblLastname,gbc);
        setPosition(0,2);
        panelAddClient.add(lblCustomerID,gbc);
        setPosition(0,3);
        panelAddClient.add(lblAge,gbc);
        setPosition(0,4);
        panelAddClient.add(lblDietPlan,gbc);
        setPosition(0,5);
        panelAddClient.add(lblWorkoutPlan,gbc);
        setPosition(0,6);
        panelAddClient.add(btnRegister,gbc);
        setPosition(1,6);
        panelAddClient.add(btnBack4,gbc);