🪲 Fix incorrect parson validation (#5703)

Fixes #5430
In puzzles, sometime the second exercise is not validated correctly because hidden elements get in the way of the correctness check.

**How to test**
Open the puzzle of level 5 and do the first exercise. Go to the second exercise and try to submit a correct answer.

static/js/appbundle.js

@@ -103861,8 +103861,10 @@ def note_with_error(value, err):
     let code = "";
     let order = new Array();
     let mistake = false;
+    let hiddenElementsCount = 0;
     document.querySelectorAll("#parsons_code_container > div > div").forEach((element, key) => {
       if (!$(element).is(":visible")) {
+        hiddenElementsCount += 1;
         return;
       }
       const parent = element.parentElement;
@@ -103873,7 +103875,7 @@ def note_with_error(value, err):
       parent.classList.remove("border-green-500");
       parent.classList.remove("border-red-500");
       const index3 = element.dataset["index"] || 999;
-      if (index3 == key + 1) {
+      if (index3 == key + 1 - hiddenElementsCount) {
         parent.classList.add("border-green-500");
       } else {
         mistake = true;

static/js/parsons.ts

@@ -116,9 +116,11 @@ export function get_parsons_code() {
     let code = "";
     let order = new Array();
     let mistake = false;
+    let hiddenElementsCount = 0;
     document.querySelectorAll<HTMLElement>('#parsons_code_container > div > div').forEach((element, key) => {        
      // We are not interested in elements that are hidden
       if (!$(element).is(':visible')) {
+        hiddenElementsCount += 1;
         return;
       }
       // the parent is the one that has the borders...
@@ -131,7 +133,7 @@ export function get_parsons_code() {
       parent.classList.remove('border-green-500');
       parent.classList.remove('border-red-500');
       const index = element.dataset['index'] || 999;
-      if (index == key + 1) {
+      if (index == key + 1 - hiddenElementsCount) {
         parent.classList.add('border-green-500');
       } else {
         mistake = true;
@@ -172,4 +174,4 @@ export function initializeParsons() {
         const editor = editorCreator.initializeReadOnlyEditor(container as HTMLElement, 'ltr');
         editorDict[i + 1] = editor;
     })
-}
+}