CInbox won't start, if dangling symlink is present as item-folder.

[pjotrek-b]

When using symlinks for Item folders, one may get this error:

Removing finished Items older than 10 days...
ERROR  Error during Inbox execution:
ERROR  SplFileInfo::getMTime(): stat failed for /srv/cinbox-data/audio/DAT/done/A0001-DAT01

This happens when the symlink is dangling.
Either the target does not exist (anymore), or it's out of reach due to insufficient permissions.

TODO: Handle and intercept this gracefully.
Currently any such invalid symlinks causes the CInbox to fail to start at all.