Hi, I was testing the contact page of my website (I'm using the latest version of osclass and the epsilon theme), and I have enabled the user to attach files, but the problem is that when I want to contact without sending an attachment, I get the message "The file you tried to upload does not have a valid extension". What could be this problem?

Files on contact form are restricted by mime type.

More details in file:
oc-includes\osclass\controller\contact.php


            $mime_array = array(
              'text/php',
              'text/x-php',
              'application/php',
              'application/x-php',
              'application/x-httpd-php',
              'application/x-httpd-php-source',
              'application/x-javascript'
           );

The problem is that I'm not attaching any files and I still get the error.

That is interesting, in such case I recommend you to disable attachments.