BUG: Fixed the runtime crash of VideoSourceTest on OSX 10.6
BUG: Fixed the runtime crash of VideoSourceTest on OSX 10.6

- Fixed the runtime crash of VideoSourceTest by avoiding division by
  zero.

- This crash was reported at the following page:
  https://open.cdash.org/testDetails.php?test=400577402&build=4162548

Change-Id: Ib0f36acb0f50f165eabc6d84ea8f4eaf796b8850

fbudin69500/ITK,vfonov/ITK,jcfr/ITK,hjmjohnson/ITK,PlutoniumHeart/ITK,Kitware/ITK,PlutoniumHeart/ITK,richardbeare/ITK,stnava/ITK,blowekamp/ITK,zachary-williamson/ITK,fbudin69500/ITK,PlutoniumHeart/ITK,richardbeare/ITK,malaterre/ITK,vfonov/ITK,richardbeare/ITK,malaterre/ITK,spinicist/ITK,fbudin69500/ITK,zachary-williamson/ITK,malaterre/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,malaterre/ITK,fbudin69500/ITK,hjmjohnson/ITK,vfonov/ITK,stnava/ITK,fbudin69500/ITK,PlutoniumHeart/ITK,thewtex/ITK,Kitware/ITK,fbudin69500/ITK,LucasGandel/ITK,thewtex/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,PlutoniumHeart/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,zachary-williamson/ITK,LucasGandel/ITK,Kitware/ITK,zachary-williamson/ITK,stnava/ITK,jcfr/ITK,vfonov/ITK,blowekamp/ITK,blowekamp/ITK,LucasGandel/ITK,spinicist/ITK,LucasGandel/ITK,jcfr/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,malaterre/ITK,spinicist/ITK,vfonov/ITK,zachary-williamson/ITK,jcfr/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,hjmjohnson/ITK,BRAINSia/ITK,BRAINSia/ITK,BRAINSia/ITK,blowekamp/ITK,stnava/ITK,stnava/ITK,jcfr/ITK,stnava/ITK,malaterre/ITK,InsightSoftwareConsortium/ITK,spinicist/ITK,blowekamp/ITK,Kitware/ITK,PlutoniumHeart/ITK,PlutoniumHeart/ITK,spinicist/ITK,spinicist/ITK,Kitware/ITK,stnava/ITK,Kitware/ITK,thewtex/ITK,hjmjohnson/ITK,BRAINSia/ITK,jcfr/ITK,BRAINSia/ITK,BRAINSia/ITK,thewtex/ITK,PlutoniumHeart/ITK,hjmjohnson/ITK,stnava/ITK,jcfr/ITK,stnava/ITK,LucasGandel/ITK,spinicist/ITK,thewtex/ITK,blowekamp/ITK,blowekamp/ITK,blowekamp/ITK,fbudin69500/ITK,malaterre/ITK,vfonov/ITK,BRAINSia/ITK,jcfr/ITK,vfonov/ITK,hjmjohnson/ITK,thewtex/ITK,LucasGandel/ITK,LucasGandel/ITK,zachary-williamson/ITK,zachary-williamson/ITK,richardbeare/ITK,malaterre/ITK,vfonov/ITK,fbudin69500/ITK,zachary-williamson/ITK,spinicist/ITK,zachary-williamson/ITK,spinicist/ITK,malaterre/ITK,hjmjohnson/ITK