rm old tag

GUI/Model/Sample/SampleItem.cpp

@@ -151,7 +151,7 @@ void SampleItem::readFrom(QXmlStreamReader* r)
             m_cross_correlation_length.readFrom2(r, tag);
         else if (tag == Tag::ExternalField)
             XML::readTaggedElement(r, tag, m_external_field);
-        else if (tag == Tag::MaterialsSet || tag == "MaterialModel" /*v<=21*/)
+        else if (tag == Tag::MaterialsSet)
             XML::readTaggedElement(r, tag, m_materials);
         else if (tag == Tag::Layer)
             XML::readTaggedElement(r, tag, *createLayerItemAt());