CI 3.1.0 Email Lib producting empty attachments

Hi.

I was recently upgrading an application to CI 3.1.0. Since that the mail reports that are generated via cronjob by that application and usually contain an excel file as attachment show said attachment as an empty file. Rolling back to the email lib of CI 3.0.4 (replacing the one in 3.1.0 keeping 3.1.0 otherwise intact) solved the issue. Can someone take a look at this?

Thanks.

A. Runzer