Update class-sv-wp-background-job-handler.php

Make this more efficient. 

While awaiting a dedicated database table where no LIKE queries ever will be needed.

Author: ramonfincken

woocommerce/utilities/class-sv-wp-background-job-handler.php

@@ -203,10 +203,11 @@ protected function is_queue_empty() {
 		$processing = '%"status":"processing"%';
 
 		$count = $wpdb->get_var( $wpdb->prepare( "
-			SELECT COUNT(*)
+			SELECT COUNT(option_id)
 			FROM {$wpdb->options}
 			WHERE option_name LIKE %s
 			AND ( option_value LIKE %s OR option_value LIKE %s )
+   			LIMIT 1
 		", $key, $queued, $processing ) );
 
 		return ( $count > 0 ) ? false : true;