contentBottom property Null safety
The vertical distance from the Scaffold's origin to the bottom of Scaffold.body.
This is useful in a FloatingActionButtonLocation designed to place the FloatingActionButton at the bottom of the screen, while keeping it above the BottomSheet, the Scaffold.bottomNavigationBar, or the keyboard.
The Scaffold.body is laid out with respect to minInsets already. This means that a FloatingActionButtonLocation does not need to factor in EdgeInsets.bottom of minInsets when aligning a FloatingActionButton to contentBottom.
final double contentBottom;