Iterate over a const copy list of containers

This effectively reverts the mutable iterations approach on
2448f88c5f, and fix crashes
and ghost items when using the filter bar

BUG: 428374

src/kitemviews/kfileitemmodel.cpp

@@ -919,9 +919,9 @@ void KFileItemModel::slotCompleted()
         // Note that the parent folder must be expanded before any of its subfolders become visible.
         // Therefore, some URLs in m_restoredExpandedUrls might not be visible yet
         // -> we expand the first visible URL we find in m_restoredExpandedUrls.
-        QMutableSetIterator<QUrl> it(m_urlsToExpand);
-        while (it.hasNext()) {
-            const QUrl url = it.next();
+        // Iterate over a const copy because items are deleted and inserted within the loop
+        const auto urlsToExpand = m_urlsToExpand;
+        for(const QUrl &url : urlsToExpand) {
             const int indexForUrl = index(url);
             if (indexForUrl >= 0) {
                 m_urlsToExpand.remove(url);

src/kitemviews/kfileitemmodelrolesupdater.cpp

@@ -957,9 +957,9 @@ void KFileItemModelRolesUpdater::updateChangedItems()
     QList<int> visibleChangedIndexes;
     QList<int> invisibleChangedIndexes;
 
-    QMutableSetIterator<KFileItem> it(m_changedItems);
-    while (it.hasNext()) {
-        const KFileItem item = it.next();
+    // Iterate over a const copy because items are deleted within the loop
+    const auto changedItems = m_changedItems;
+    for (const KFileItem item : changedItems) {
         const int index = m_model->index(item);
 
         if (index < 0) {

src/kitemviews/kitemlistview.cpp

@@ -1155,10 +1155,10 @@ void KItemListView::slotItemsRemoved(const KItemRangeList& itemRanges)
         QVector<int> itemsToMove;
 
         // Remove all KItemListWidget instances that got deleted
-        QMutableHashIterator<int, KItemListWidget*> it(m_visibleItems);
-        while (it.hasNext()) {
-            it.next();
-            KItemListWidget* widget = it.value();
+        // Iterate over a const copy because the container is mutated within the loop
+        // directly and in `recycleWidget()` (https://bugs.kde.org/show_bug.cgi?id=428374)
+        const auto visibleItems = m_visibleItems;
+        for (KItemListWidget* widget : visibleItems) {
             const int i = widget->index();
             if (i < firstRemovedIndex) {
                 continue;