How to change value if user changed picture

I want to Gives for Fb_image value 0 only if user changed his profile picture.

if just pressed save settings for something like full name without changing picture it stays same of database.

In this code fb_image = 0even if user didn’t change the picture.

// upload users image
        $filename_image = null;
        if(! empty($_FILES['image']['name']) ) // if image 
        {
            $file_image         = array('folder'=>'users/images', 'input_file'=>'image');
            // update users image
            $filename_image     = $this->file_uploads->upload_file($file_image, 512, 512, 256, 256);
            // through image upload error
            if(!empty($filename_image['error']))
                $this->form_validation->set_rules('image_error', lang('common_image'), 'required', array('required'=>$filename_image['error']));
        }

        if ($this->form_validation->run() === TRUE)
        {
            // save the changes
            $data                       = array();

            // upload image only if selected
            if(!empty($filename_image) && !isset($filename_image['error']))
                $data['image']          = $filename_image;
                $data['fb_image']       = 0 ;
                

            $data['fullname']           = $this->input->post('fullname');
            $data['email']              = $this->input->post('email');
            $data['username']           = $this->input->post('username');
            $data['gender']             = $this->input->post('gender');
            $data['notifications']      = isset($_POST['notifications']) ? 1 : 0;
            $data['apppear_search']     = isset($_POST['apppear_search']) ? 1 : 0;
            $data['anonymous_posts']    = isset($_POST['anonymous_posts']) ? 1 : 0;