RecordNumber peek() {
			RecordNode node = getTop();
			if (node == tail) {
				return null;
			}
			return node.recordNumber;
		}
Peek at top node
@return the node's record number or {@code null} if there are no nodes left
Ghidra/Features/PDB/src/main/java/ghidra/app/util/pdb/pdbapplicator/MultiphaseDataTypeResolver.java