Recently activated material can no longer be removed

CURA-3147

resources/qml/Preferences/MaterialsPage.qml

@@ -128,7 +128,11 @@ UM.ManagementPage
             text: catalog.i18nc("@action:button", "Activate");
             iconName: "list-activate";
             enabled: base.currentItem != null && base.currentItem.id != Cura.MachineManager.activeMaterialId && Cura.MachineManager.hasMaterials
-            onClicked: Cura.MachineManager.setActiveMaterial(base.currentItem.id)
+            onClicked:
+            {
+                Cura.MachineManager.setActiveMaterial(base.currentItem.id)
+                currentItem = base.model.getItem(base.objectList.currentIndex) // Refresh the current item.
+            }
         },
         Button
         {