Add ExtruderStack to GlobalStack in single extrusion machine fix

cura/Settings/ExtruderManager.py

@@ -374,6 +374,8 @@ class ExtruderManager(QObject):
             extruder_definition = container_registry.findDefinitionContainers(id = expected_extruder_definition_0_id)[0]
             extruder_stack_0.definition = extruder_definition
 
+        extruder_stack_0.setNextStack(global_stack)
+
     ##  Get all extruder values for a certain setting.
     #
     #   This is exposed to qml for display purposes