Add null pointer check

[sim051277]

Adding and using this library in my project caused a null pointer exception crash for the following line . Hence adding the null pointer check as safe guard
private int getTopForViewRelativeOnlyChild(View v) {
int top = v.getTop();
while (v.getParent() != getChildAt(0)) {
v = (View) v.getParent();
top += v.getTop(); //Null pointer exception here ,
}
return top;
}