cmpsvg repeatedly crashes during build of 'ubuntu-mono' icon set

'cmpsvg' and 'scour.py' crash a few dozen times when building the 'ubuntu-mono' icon set.

  Traceback (most recent call last):
    File "/usr/share/python-scour/cmpsvg", line 49, in <module>
      diff /= float(sum(d1))
  ZeroDivisionError: float division by zero
  dh_scour: scour was not able to process nm-wwan-tower.svg

It's like playing whack-a-mole if you're on a desktop machine with 'apport-gtk' popping up once every five seconds during the build.

A workaround while building is something like:

  while true ; do sleep 1 ; killall apport-gtk ; done