Fix mark-selection-as-unread (#5367)

The "mark selection as unread" button would mark articles as read instead of unread...

app/layout/nav_menu.phtml

@@ -132,7 +132,7 @@
 		);
 
 		$mark_unread_url = $mark_read_url;
-		$mark_unread_url['params']['is_read'] = false;
+		$mark_unread_url['params']['is_read'] = '0';
 		$mark_unread_url['params']['nextGet'] = $get;
 	?>