BottomAppBar constructor Null safety
Creates a bottom application bar.
The clipBehavior argument defaults to Clip.none and must not be null. Additionally, elevation must be non-negative.
If color, elevation, or shape are null, their BottomAppBarTheme values will be used. If the corresponding BottomAppBarTheme property is null, then the default specified in the property's documentation will be used.
Implementation
const BottomAppBar({
  super.key,
  this.color,
  this.elevation,
  this.shape,
  this.clipBehavior = Clip.none,
  this.notchMargin = 4.0,
  this.child,
}) : assert(elevation == null || elevation >= 0.0),
     assert(notchMargin != null),
     assert(clipBehavior != null);