Fixes this error:
Undefined subroutine &main::MarkIssueReturned called at
misc/cronjobs/longoverdue.pl line 316.
Signed-off-by: Josef Moravec <josef.moravec@gmail.com> Signed-off-by: Julian Maurice <julian.maurice@biblibre.com> Signed-off-by: Nick Clemens <nick@bywatersolutions.com>