Properly detect and handle empty address lists

The mainly comes in when a MIME header which might contain a list of email
addresses (like Reply-To) is to be parsed, but is empty. The Mail_RFC822
class would return an empty mailbox @ localhost (where 'localhost' is the
default default_domain for mail address list parsing).

include/class.mailparse.php

@@ -264,6 +264,8 @@ class Mail_Parse {
     }
 
     function parseAddressList($address){
+        if (!$address)
+            return false;
         return Mail_RFC822::parseAddressList($address, null, null,false);
     }