fix 2 warnings in feed editor

classes/pref/feeds.php

@@ -996,8 +996,8 @@ class Pref_Feeds extends Handler_Protected {
 		$feed_title = clean($_POST["title"]);
 		$feed_url = clean($_POST["feed_url"]);
 		$site_url = clean($_POST["site_url"]);
-		$upd_intl = (int) clean($_POST["update_interval"]);
-		$purge_intl = (int) clean($_POST["purge_interval"]);
+		$upd_intl = (int) clean($_POST["update_interval"] ?? 0);
+		$purge_intl = (int) clean($_POST["purge_interval"] ?? 0);
 		$feed_id = (int) clean($_POST["id"] ?? 0); /* editSave */
 		$feed_ids = explode(",", clean($_POST["ids"] ?? "")); /* batchEditSave */
 		$cat_id = (int) clean($_POST["cat_id"]);