Bug 29078: Resolve division by zero in touch_all scripts

Bug 29078: Resolve division by zero in touch_all scripts

Illegal division by zero at misc/maintenance/touch_all_biblios.pl line 102.

Trivial fix.
Funny that the percentage is not even shown without verbose flag ;)

Test plan:
Run misc/maintenance/touch_all_biblios.pl -where 'biblionumber<0'
You should now see:
Good: 0, Bad: 0 (of 0) in 0 seconds

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>