whenOrNull<TResult extends Object?>  method 
- @optionalTypeArgs
- TResult? $default(- ReownAppKitModalColors lightColors,
- ReownAppKitModalColors darkColors,
- ReownAppKitModalTextStyles textStyles,
- ReownAppKitModalRadiuses radiuses,
 
A variant of when that fallback to returning null
It is equivalent to doing:
switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case _:
    return null;
}
Implementation
@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? Function( ReownAppKitModalColors lightColors,  ReownAppKitModalColors darkColors,  ReownAppKitModalTextStyles textStyles,  ReownAppKitModalRadiuses radiuses)?  $default,) {final _that = this;
switch (_that) {
case _ReownAppKitModalThemeData() when $default != null:
return $default(_that.lightColors,_that.darkColors,_that.textStyles,_that.radiuses);case _:
  return null;
}
}