Thesis 1.8 and PHP 5.4

I keep getting the following warning when saving a post:

Warning: Illegal string offset ‘type’ in /home/property/public_html/wp-content/themes/thesis_18/lib/admin/options_post.php on line 151

Line 151 is this:

// If we reach this point in the code, that means we're authenticated. Proceed with saving the new data
		foreach ($post_options->meta_boxes as $meta_box) {
			foreach ($meta_box['fields'] as $meta_field) {
				$current_data = get_post_meta($post_id, $meta_field['name'], true);
				$new_data = $_POST[$meta_field['name']];

				<strong>if (($meta_field['type']['type'] == 'checkbox') && is_array($meta_field['type']['options'])) {</strong><em>
					foreach ($meta_field['type']['options'] as $option_name => $option) {
						if ((bool) $new_data[$option_name] != (bool) $option['default'])
							$new_data[$option_name] = (bool) $new_data[$option_name];
						elseif ((bool) $new_data[$option_name] == (bool) $option['default'])
							unset($new_data[$option_name]);
					}

					if ($new_data)
						update_post_meta($post_id, $meta_field['name'], $new_data);
					else
						delete_post_meta($post_id, $meta_field['name']);
				}
				else {
					if ($current_data) {
						if ($new_data == '')
							delete_post_meta($post_id, $meta_field['name']);
						elseif ($new_data == $meta_field['default'])
							delete_post_meta($post_id, $meta_field['name']);
						elseif ($new_data != $current_data)
							update_post_meta($post_id, $meta_field['name'], $new_data);
					}
					elseif ($new_data != '')
						add_post_meta($post_id, $meta_field['name'], $new_data, true);
				}
			}
		}
	}

Does anyone know of a modification to this code to stop the warnings?