List replace by condition to Empty List Item

[ruben.romero]

@Vikram_Subbaiah

def emp (a:var[]..[])
{
	return [Imperative]
	{
		b = [];
		for (i in a)
		{
			if (i < 0)
			{
				return List.Empty;
			}
			else
			{
				return i;
			}
		}
	}
};

I tried to modify it to replace Empty List by a string but not lucky, get Null results instead.