toListOrEmpty method
Wraps a non-null value in a single-element list, or returns an empty list when null.
Distinct from MakeListExtensions.toListIfNotNull, which returns null
(not an empty list) for a null receiver. Renamed from toListIfNotNull to
avoid an ambiguous-extension clash with that established API and because
"if not null" wrongly implied a nullable result.
Example:
5.toListOrEmpty(); // [5]
null.toListOrEmpty(); // []
Implementation
List<T> toListOrEmpty() {
final T? self = this;
if (self == null) return <T>[];
return <T>[self];
}