Advance to the next linkage node that has a non-empty list of names.  Return the
		 * PDOMName at the head of the list.  This is the next name that should be returned
		 * from #next().  Return null if there are no more linkage nodes.
Advance to the next linkage node that has a non-empty list of names.  Return the
		 * PDOMName at the head of the list.  This is the next name that should be returned
		 * from #next().  Return null if there are no more linkage nodes. | PDOMExternalReferencesList.java