reduce SessionModel usage in LayerItem

GUI/Model/Sample/LayerItem.cpp

@@ -45,21 +45,19 @@ QVector<ItemWithMaterial*> layoutItemsWithMaterial(ParticleLayoutItem* item)
         if (!item)
             continue;
 
-        if (item->hasModelType<ParticleCompositionItem>())
-            itemsWithParticles << polymorphic_cast<ParticleCompositionItem*>(item)->particles();
-        else if (item->hasModelType<MesoCrystalItem>())
-            itemsWithParticles << polymorphic_cast<MesoCrystalItem*>(item)->basisParticle();
-        else if (item->hasModelType<ParticleItem>())
-            ret << dynamic_cast<ParticleItem*>(item);
-        else if (item->hasModelType<ParticleCoreShellItem>()) {
-            if (auto* core = dynamic_cast<ParticleCoreShellItem*>(item)->core())
-                ret << core;
-            if (auto* shell = dynamic_cast<ParticleCoreShellItem*>(item)->shell())
-                ret << shell;
+        if (auto* p = dynamic_cast<ParticleCompositionItem*>(item))
+            itemsWithParticles << p->particles();
+        else if (auto* p = dynamic_cast<MesoCrystalItem*>(item))
+            itemsWithParticles << p->basisParticle();
+        else if (auto* p = dynamic_cast<ParticleItem*>(item))
+            ret << p;
+        else if (auto* p = dynamic_cast<ParticleCoreShellItem*>(item)) {
+            if (p->core())
+                ret << p->core();
+            if (p->shell())
+                ret << p->shell();
         } else
-            throw Error("Error in GUI::MaterialUtil::materialProperties: cannot handle "
-                        "passed model type '"
-                        + item->modelType() + "'");
+            ASSERT(false);
     }
     return ret;
 }