BUG: Guard against Divide by Zero

As identified in https://issues.itk.org/jira/browse/ITK-3179

Potential divide by zero related to use of the
ImageScanLineIterator.

Change-Id: I7d85e9b79188eaf3dcc32ce033d07ca1d5336f9d
Merge topic 'DivideByZeroCheck-3179'

b3fa1d5 BUG: Guard against Divide by Zero