protect against a divide-by-zero, set up event callbacks to work with nested ds arrays

10 jobs for nested-ds-events in 319 minutes and 30 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Test
passed debian_stable_amd64_deb #6707
debian stable amd64

00:32:10

passed debian_stable_arm_deb #6715
debian arm stable

00:37:13

passed debian_stable_i386_deb #6706
debian stable i386

00:38:43

passed debian_stretch_amd64_deb #6708
debian stretch amd64

00:30:16

passed osx_10.8_amd64_dmg #6713
osx v10.8 dmg

00:21:15

passed osx_amd64_dmg #6712
osx v10.11 dmg

00:20:04

passed ubuntu_14.04_amd64_deb #6710
ubuntu v14.04 amd64

00:31:01

passed ubuntu_14.04_i386_deb #6709
ubuntu v14.04 i386

00:34:42

passed ubuntu_16.04_amd64_deb #6711
ubuntu v16.04 amd64

00:38:19

passed windows_i386_installer #6714
windows i386

01:12:53