[BUGFIX] sonarcloud javascript:S6582 fixed.

Prefer using an optional chain expression instead, as it's more concise and easier to read.

Author: Gonzalo Diaz

src/projecteuler/lib/BNodeBuilder.js

@@ -34,7 +34,7 @@ export default class BNodeBuilder extends BNode {
     if (dataTree[i]?.[j]) {
       const resultNode = new BNode(dataTree[i][j] + rootValue);
 
-      if (dataTree[i + 1] && dataTree[i + 1][j] && dataTree[i + 1][j + 1]) {
+      if (dataTree?.[i + 1]?.[j] && dataTree?.[i + 1]?.[j + 1]) {
         // Next left coordinates: [i + 1][j]
         resultNode.setLeft(
           BNodeBuilder.buildBNodeTreeWeigth(