Show extruder as disabled if either material or core is missing

It basically just means you can't print with it.

Contributes to issue CURA-5876.

resources/qml/Menus/ConfigurationMenu/PrintCoreConfiguration.qml

@@ -24,6 +24,7 @@ Row
         {
             materialColor: printCoreConfiguration.material.color
             anchors.verticalCenter: parent.verticalCenter
+            extruderEnabled: printCoreConfiguration.material.name !== "" && printCoreConfiguration.hotendID !== ""
         }
     }