The ASObjectList interface provides the abstraction of an
ordered collection of AS nodes, without defining or constraining how this
collection is implemented. ASObjectList objects in the DOM
AS are live.
Returns the indexth item in the collection. The index
starts at 0. If index is greater than or equal to the
number of nodes in the list, this returns null.
param
index index into the collection.
return
The ASObject at the indexth position
in the ASObjectList, or null if that is
not a valid index.