trivial conversion out of lambda

GUI/Model/Data/DataItem.cpp

@@ -129,11 +129,9 @@ void DataItem::saveDatafield(const QString& projectDir) const
     std::unique_lock<std::mutex> lock(m_update_data_mutex); // TODO why lock??
     auto* clone = converted_field()->clone();
     lock.unlock();
+    std::unique_ptr<Datafield> field(clone); // for memory management
 
-    auto saveLambda = [clone, path] {
-        std::unique_ptr<Datafield> field(clone); // for memory management
-        IOFactory::writeDatafield(*field, path.toStdString());
-    };
+    auto saveLambda = [&field, path] { IOFactory::writeDatafield(*field, path.toStdString()); };
 
     if (m_saveInBackground) {
         std::string errorMessage;