function zTaxonomyColumns error

Please update your zTaxonomyColumns method with this suggested fix

function zTaxonomyColumns( $columns ) {
	$new_columns = array();

	// Keep checkbox column if it exists
	if ( isset( $columns['cb'] ) ) {
		$new_columns['cb'] = $columns['cb'];
		unset( $columns['cb'] );
	}

	// Add image column
	$new_columns['thumb'] = __( 'Image', 'categories-images' );

	// Merge back the rest of the columns
	return array_merge( $new_columns, $columns );
}