fix error on GCC

GUI/Model/Project/ProjectDocument.cpp

@@ -349,7 +349,8 @@ ProjectDocument::ReadResult ProjectDocument::readProject(QIODevice* device,
                         m_materials.readContentFrom(&reader);
                         GUI::Session::XML::assertExpectedTag(&reader, MaterialsTag);
                     } else if (reader.name() == SamplesTag) {
-                        m_samples.serialize(Serializer(&reader));
+                        Serializer s(&reader);
+                        m_samples.serialize(s);
                         // cleanup
                         if (reader.name() != SamplesTag) {
                             if (!reader.isEndElement())
@@ -414,7 +415,8 @@ void ProjectDocument::writeTo(QIODevice* device)
     writer.writeEndElement();
 
     writer.writeStartElement(SamplesTag);
-    m_samples.serialize(Serializer(&writer));
+    Serializer s(&writer);
+    m_samples.serialize(s);
     writer.writeEndElement();
 
     m_applicationModels.writeTo(&writer);