How is it possible that neither if nor else branch gets executed here? I'm developing one of my first drupal modules and stuck here:

$maxexp = db_result(db_query("SELECT max(expiration) FROM {uc_roles_expirations} WHERE UID=%d and rid=%d", $uid_befizeto, 4));
dpm('DB query finished');
dpm('me = '.$maxexp);

if($maxexp) {
   dpm('True branch');
 } else {
   dpm('False branch');
 }


This is a snippet from mymodule_nodeapi's case 'insert'. My problem is that I do not understand why do I see the following messages after saving a node:

DB query finished
me = 
Node blah saved successfully


I simply do not understand if there is no error, how it is possible that I cannot see True branch or False branch among the messages..
It was a character encoding problem in the source file. I changed the encoding in my favorite  text editor, and the code started working.