warning on uc_bitcoin.module on line 139

I get this error at checkout:
warning: strstr() [function.strstr]: Empty delimiter in /var/www/html/drupal-6.24/modules/uc_bitcoin.module on line 139.
I am using drupal version 6.24
line 139 of uc_bitcoin.modules is the following:
if ($message['id'] == 'uc_order_action-mail' && !strstr(uc_store_email_from(), $message['to'])) {

I do get at checkout a bitcoin address where to send the coin, but the problem is that the digital download file becomes available immediately after checkout, so if the buyer does not send the bitcoins he can still download the file without payment.

Something is clearly wrong in my configuration, I have followed the instructions on the nostate page already, any help provided will be greatly appreciated, I also followed the instructions on http://www.ubercart.org/docs/user/10966/selling_files, the problem is that the files become available without having to pay.

I am trying to sell digital goods, where the digital good is a file that contains a number, this number represents telephone credit, just like a calling card.

Anyone else also having this problem?