No message/feedback-report part causes abort

Currently, if a message in `id_list` doesn't have a message/feedback-report part, it will cause the script to abort immediately. If this is early in the list, it causes mails to be dropped.

This patch initializes `feedbackreportitems` so that a bad mail is non-fatal.
Merge pull request #7 from worr/patch-3

No message/feedback-report part causes abort