BUG: Fix valgrind error for VideoSourceTest.
BUG: Fix valgrind error for VideoSourceTest.

Fix the valgrind error in VideoSourceTest (
"Uininitialized Memory Read"): need to check
whether the frame image is empty before checking
the pixel value..

Change-Id: I86ca613c0febafc7b52405f9892311539f5d616e

zachary-williamson/ITK,LucasGandel/ITK,blowekamp/ITK,LucasGandel/ITK,paulnovo/ITK,blowekamp/ITK,hendradarwin/ITK,BRAINSia/ITK,rhgong/itk-with-dom,zachary-williamson/ITK,stnava/ITK,eile/ITK,hendradarwin/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,GEHC-Surgery/ITK,hendradarwin/ITK,stnava/ITK,spinicist/ITK,LucHermitte/ITK,fuentesdt/InsightToolkit-dev,LucasGandel/ITK,msmolens/ITK,paulnovo/ITK,BlueBrain/ITK,thewtex/ITK,hinerm/ITK,hendradarwin/ITK,fuentesdt/InsightToolkit-dev,GEHC-Surgery/ITK,atsnyder/ITK,thewtex/ITK,malaterre/ITK,Kitware/ITK,eile/ITK,rhgong/itk-with-dom,jmerkow/ITK,richardbeare/ITK,BRAINSia/ITK,jcfr/ITK,fbudin69500/ITK,BRAINSia/ITK,fedral/ITK,malaterre/ITK,PlutoniumHeart/ITK,biotrump/ITK,hjmjohnson/ITK,stnava/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,LucasGandel/ITK,eile/ITK,msmolens/ITK,PlutoniumHeart/ITK,BlueBrain/ITK,blowekamp/ITK,Kitware/ITK,biotrump/ITK,malaterre/ITK,fbudin69500/ITK,fuentesdt/InsightToolkit-dev,Kitware/ITK,msmolens/ITK,heimdali/ITK,msmolens/ITK,LucHermitte/ITK,stnava/ITK,eile/ITK,InsightSoftwareConsortium/ITK,jmerkow/ITK,fedral/ITK,stnava/ITK,LucasGandel/ITK,spinicist/ITK,paulnovo/ITK,spinicist/ITK,vfonov/ITK,paulnovo/ITK,heimdali/ITK,BlueBrain/ITK,heimdali/ITK,richardbeare/ITK,eile/ITK,jcfr/ITK,thewtex/ITK,BRAINSia/ITK,GEHC-Surgery/ITK,vfonov/ITK,blowekamp/ITK,vfonov/ITK,jcfr/ITK,thewtex/ITK,paulnovo/ITK,spinicist/ITK,zachary-williamson/ITK,biotrump/ITK,rhgong/itk-with-dom,heimdali/ITK,fuentesdt/InsightToolkit-dev,malaterre/ITK,InsightSoftwareConsortium/ITK,GEHC-Surgery/ITK,zachary-williamson/ITK,jcfr/ITK,fedral/ITK,thewtex/ITK,jmerkow/ITK,fedral/ITK,spinicist/ITK,hjmjohnson/ITK,blowekamp/ITK,richardbeare/ITK,jmerkow/ITK,hinerm/ITK,hinerm/ITK,fedral/ITK,rhgong/itk-with-dom,hjmjohnson/ITK,atsnyder/ITK,hjmjohnson/ITK,vfonov/ITK,hjmjohnson/ITK,paulnovo/ITK,hinerm/ITK,fuentesdt/InsightToolkit-dev,atsnyder/ITK,jmerkow/ITK,jcfr/ITK,fbudin69500/ITK,PlutoniumHeart/ITK,BRAINSia/ITK,malaterre/ITK,hinerm/ITK,BlueBrain/ITK,richardbeare/ITK,eile/ITK,msmolens/ITK,GEHC-Surgery/ITK,richardbeare/ITK,fbudin69500/ITK,malaterre/ITK,Kitware/ITK,ajjl/ITK,heimdali/ITK,ajjl/ITK,malaterre/ITK,zachary-williamson/ITK,malaterre/ITK,fedral/ITK,GEHC-Surgery/ITK,atsnyder/ITK,thewtex/ITK,hendradarwin/ITK,heimdali/ITK,blowekamp/ITK,BRAINSia/ITK,spinicist/ITK,hendradarwin/ITK,vfonov/ITK,rhgong/itk-with-dom,atsnyder/ITK,fuentesdt/InsightToolkit-dev,PlutoniumHeart/ITK,jmerkow/ITK,PlutoniumHeart/ITK,zachary-williamson/ITK,stnava/ITK,fedral/ITK,ajjl/ITK,fuentesdt/InsightToolkit-dev,spinicist/ITK,biotrump/ITK,GEHC-Surgery/ITK,LucHermitte/ITK,BlueBrain/ITK,jcfr/ITK,BlueBrain/ITK,atsnyder/ITK,stnava/ITK,spinicist/ITK,PlutoniumHeart/ITK,jmerkow/ITK,jmerkow/ITK,ajjl/ITK,heimdali/ITK,ajjl/ITK,PlutoniumHeart/ITK,atsnyder/ITK,LucHermitte/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,stnava/ITK,jcfr/ITK,rhgong/itk-with-dom,paulnovo/ITK,rhgong/itk-with-dom,zachary-williamson/ITK,heimdali/ITK,blowekamp/ITK,atsnyder/ITK,fedral/ITK,fbudin69500/ITK,LucHermitte/ITK,GEHC-Surgery/ITK,fbudin69500/ITK,eile/ITK,BRAINSia/ITK,fuentesdt/InsightToolkit-dev,zachary-williamson/ITK,hjmjohnson/ITK,hendradarwin/ITK,stnava/ITK,thewtex/ITK,hinerm/ITK,LucHermitte/ITK,fuentesdt/InsightToolkit-dev,richardbeare/ITK,vfonov/ITK,atsnyder/ITK,biotrump/ITK,msmolens/ITK,spinicist/ITK,LucHermitte/ITK,jcfr/ITK,LucHermitte/ITK,Kitware/ITK,eile/ITK,LucasGandel/ITK,hinerm/ITK,Kitware/ITK,biotrump/ITK,biotrump/ITK,rhgong/itk-with-dom,hjmjohnson/ITK,biotrump/ITK,zachary-williamson/ITK,InsightSoftwareConsortium/ITK,PlutoniumHeart/ITK,hendradarwin/ITK,fbudin69500/ITK,blowekamp/ITK,hinerm/ITK,ajjl/ITK,BlueBrain/ITK,ajjl/ITK,eile/ITK,msmolens/ITK,LucasGandel/ITK,ajjl/ITK,vfonov/ITK,fbudin69500/ITK,richardbeare/ITK,msmolens/ITK,BlueBrain/ITK,vfonov/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,hinerm/ITK,paulnovo/ITK