Get extruders list from GlobalStack itself

CURA-4784

plugins/CuraEngineBackend/CuraEngineBackend.py

@@ -722,7 +722,7 @@ class CuraEngineBackend(QObject, Backend):
         if self._global_container_stack:
             self._global_container_stack.propertyChanged.disconnect(self._onSettingChanged)
             self._global_container_stack.containersChanged.disconnect(self._onChanged)
-            extruders = list(ExtruderManager.getInstance().getMachineExtruders(self._global_container_stack.getId()))
+            extruders = list(self._global_container_stack.extruders.values())
 
             for extruder in extruders:
                 extruder.propertyChanged.disconnect(self._onSettingChanged)
@@ -733,7 +733,7 @@ class CuraEngineBackend(QObject, Backend):
         if self._global_container_stack:
             self._global_container_stack.propertyChanged.connect(self._onSettingChanged)  # Note: Only starts slicing when the value changed.
             self._global_container_stack.containersChanged.connect(self._onChanged)
-            extruders = list(ExtruderManager.getInstance().getMachineExtruders(self._global_container_stack.getId()))
+            extruders = list(self._global_container_stack.extruders.values())
             for extruder in extruders:
                 extruder.propertyChanged.connect(self._onSettingChanged)
                 extruder.containersChanged.connect(self._onChanged)