the submit confirmation mail for the task course element doesn't work very well in the case of submissions without a file, which happens from time to time.
In order to prevent such mails:
The submission of the file "$filename" for Andreas Muster (firstname.lastname@example.org) at 04.11.2015 has been confirmed.
we should adapt
1) the mail template text
2) the way OO handles the variable "$filename" in case there was no file
Hiermit wird bestätigt, dass $first $last ($email) die Datei "$filename" am $date um $time hochgeladen hat.
Hiermit wird bestätigt, dass $first $last ($email) [number of files] Datei(en) ($filename) am $date um $time hochgeladen hat.
The submission of the file "$filename" for $first $last ($email) at $date has been confirmed.
The submission of [number of files] file(s) ($filename) for $first $last ($email) at $date, $time has been confirmed.
2) if the number of files = 0, the variable is not replaced in the mail. This should not happen. Therefore, if 0 files were submitted, the variable $filename should be replaced with
DE: Keine Datei hochgeladen
EN: No file uploaded
this translation should be checked against other instances where $filename is used, and reworked if necessary