Added null pointer checking.
Added null pointer checking.

KaranDagar/crystalvc,SoftwareEngineeringToolDemos/FSE-2011-Crystal,SoftwareEngineeringToolDemos/FSE-2011-Crystal,KaranDagar/FSE-2011-Crystal---old,KaranDagar/crystalvc,SoftwareEngineeringToolDemos/FSE-2011-Crystal,brunyuriy/crystalvc,KaranDagar/FSE-2011-Crystal---old,brunyuriy/crystalvc