revert back load_filters-related changes

classes/feeds.php

@@ -1848,7 +1848,7 @@ class Feeds extends Handler_Protected {
 		if ($feed) {
 			return $feed->cat_id;
 		} else {
-			return null;
+			return false;
 		}
 	}
 

classes/rssutils.php

@@ -1713,9 +1713,9 @@ class RSSUtils {
 		$filters = array();
 
 		$feed_id = (int) $feed_id;
-		$cat_id = Feeds::_cat_of_feed($feed_id);
+		$cat_id = (int)Feeds::_cat_of_feed($feed_id);
 
-		if (empty($cat_id))
+		if (!$cat_id)
 			$null_cat_qpart = "cat_id IS NULL OR";
 		else
 			$null_cat_qpart = "";