addIfNotNull method
Returns a new set with element
added if it's not null.
Example:
final set = {1, 2, 3};
print(set.addIfNotNull(4)); // Outputs {1, 2, 3, 4}
Implementation
Set<E> addIfNotNull(E? element) {
if (element == null) return this;
return {...this, element};
}