“References cannot be null,whereas pointers can; every reference refers to some object,although it may or may not be valid.”

但是我不相信因为下面的代码看它编译器没有错误：

class person
{
public:
virtual void setage()=0;
};
main()
{
person *object=NULL;
person &object1=*object;
}@H_502_9@ 
 
请详细说明这一点.