Bug 35171: Add send_empty option to runreport

Bug 35171: Add send_empty option to runreport

This patch adds a new 'send_empty' option to runreport.pl

To test:
1 - Create a report in Koha that will not return any results:
    SELECT barcode FROM items WHERE 1=2
2 - perl misc/cronjobs/runreport.pl 1
3 - Output is: NO OUTPUT: 0 results from execute_query
4 - perl misc/cronjobs/runreport.pl 1 --send_empty
5 - Output is: no results were returned for the report
6 - perl misc/cronjobs/runreport.pl 1 --send_empty --email
7 - It will die on an email error unless you have SMTP configured - this si good, it means we sent an email
8 - Bonus points: Test on a system that can correctly send emails, confirm it works :-)

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>