Fixed force-cache clearing when options updated.

No more PHP warnings triggered.

readme.txt

@@ -46,7 +46,7 @@ Many thanks for donations, contributors, supporters, testers & bug reporters:
 * Jason Miller
 * [Dave Clark](https://github.com/dkcwd)
 * Miguel Clara
-* [plescheff](https://github.com/plescheff)
+* [Anton Pelešev](https://github.com/plescheff)
 * Firas Dib
 * [CotswoldPhoto](http://wordpress.org/support/profile/cotswoldphoto)
 * [tamagokun](https://github.com/tamagokun)

wp-ffpc-class.php

@@ -860,9 +860,9 @@ class WP_FFPC extends PluginAbstract {
 			wp_clear_scheduled_hook ( self::precache_id );
 		}
 
-		/* flush the cache when news options are saved, not needed on activation */
+		/* flush the cache when new options are saved, not needed on activation */
 		if ( !$activating )
-			$this->backend->clear();
+			$this->backend->clear(null, true);
 
 		/* create the to-be-included configuration for advanced-cache.php */
 		$this->update_global_config();