#vulnerable code 
                                private void sendPushNotification(DashBoard dashBoard, Notification notification, int dashId, int deviceId) {
        Device device = dashBoard.getDeviceById(deviceId);
        final String dashName = dashBoard.name == null ? "" : dashBoard.name;
        final String deviceName = device.name == null ? "device" : device.name;
        String message = "Your " + deviceName + " went offline. \"" + dashName + "\" project is disconnected.";
        notification.push(gcmWrapper,
                message,
                dashId
        );
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private void sendPushNotification(DashBoard dashBoard, Notification notification, int dashId, int deviceId) {
        Device device = dashBoard.getDeviceById(deviceId);
        final String dashName = dashBoard.name == null ? "" : dashBoard.name;
        final String deviceName = ((device == null || device.name == null) ? "device" : device.name);
        String message = "Your " + deviceName + " went offline. \"" + dashName + "\" project is disconnected.";
        notification.push(gcmWrapper,
                message,
                dashId
        );
    }