Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 18436)
+++ wp-includes/taxonomy.php	(working copy)
@@ -850,9 +850,10 @@
 	} else {
 		if ( is_object($term) )
 			$term = $term->term_id;
-		$term = (int) $term;
+		if ( !$term = (int) $term )
+			return $null;
 		if ( ! $_term = wp_cache_get($term, $taxonomy) ) {
-			$_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND t.term_id = %s LIMIT 1", $taxonomy, $term) );
+			$_term = $wpdb->get_row( $wpdb->prepare( "SELECT t.*, tt.* FROM $wpdb->terms AS t INNER JOIN $wpdb->term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy = %s AND t.term_id = %d LIMIT 1", $taxonomy, $term) );
 			if ( ! $_term )
 				return $null;
 			wp_cache_add($term, $_term, $taxonomy);