ScxmlEditor: Fix a crash when closing scxml editor

Don't iterate on m_overlappedItems inside d'tor, as every
iteration calls removeOverlappingItem() and it modifies
the container being iterated. Do the same for m_outputTransitions
and m_inputTransitions.

Amends 8b444f88eb

Fixes: QTCREATORBUG-28027
Change-Id: I78fe67b5ea584c969e4850a2db3f00d981296865
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Artem Sokolovskii <artem.sokolovskii@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/scxmleditor/plugin_interface/scattributeitemdelegate.cpp

@@ -80,7 +80,7 @@ void SCAttributeItemDelegate::setEditorData(QWidget *editor, const QModelIndex &
             combo->clear();
             const QStringList values = index.data(DataRole).toString().split(";");
 
-            for (QString val : values)
+            for (const QString &val : values)
                 combo->addItem(val);
 
             combo->setCurrentText(index.data().toString());