RecordNumber pop() {
			RecordNode node = getTop();
			if (node == tail) {
				return null;
			}
			removeNodeLinkage(node);
			map.remove(node.recordNumber);
			numNodes--;
			if (debug) {
				debugBuilder.append(" pop:");
				debugBuilder.append(node.recordNumber);
				debugBuilder.append("\n");
				if (map.isEmpty()) {
					System.out.println(debugBuilder.toString());
				}
			}
			return node.recordNumber;
		}
Pop top node
@return the popped 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