fix oai without identifier

library/Class/WebService/OAIHarvester.php

@@ -31,7 +31,7 @@ class Class_WebService_OAIHarvester {
     IDENTIFIER_PATTERN = '|<identifier[^>]*>[^<]*</identifier>|',
     LIST_RECORDS = 'ListRecords';
 
-  public static $MAX_REQUESTS = 50000;
+  public static int $MAX_REQUESTS = 50000;
   protected
     $_base_url,
     $_query = '',