Layered Nav Widget warning array_merge()

Hi,

I added the Woocommerce Layered Nav widget manually to my shop page so that it appears as a dropdown on the top of the shop page. I did this through functions.php:

add_action( 'woocommerce_before_shop_loop', 'widgetized_shop_filter', 50 );

function widgetized_shop_filter() {
	global $woocommerce;

	echo '<form class="woocommerce-ordering" method="get">';
	the_widget('WC_Widget_Layered_Nav', 'title=&attribute=irauthor&query_type=AND&display_type=dropdown');
	echo '</form>';

}

It works fine on my test site: emaginetestbed.com/indireads/books, but on the live site, I get this error:

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in /home/xxxx/indireads.com/wp-content/plugins/woocommerce/classes/widgets/class-wc-widget-layered-nav.php on line 56

Any idea why this would happen? I have a few extra extensions on the live site than on the test site (payment gateways). But I don’t see how this affects the widget. If I call the widget into a sidebar, I have no errors. It’s just where it’s called manually.

Am on a tight schedule, so any help would be appreciated.

http://wordpress.org/extend/plugins/woocommerce/