Check if a material is being used based on base_file

CURA-4129

cura/Settings/ContainerManager.py

@@ -333,16 +333,15 @@ class ContainerManager(QObject):
     @pyqtSlot(str, result = bool)
     def isContainerUsed(self, container_id):
         Logger.log("d", "Checking if container %s is currently used", container_id)
-        # check if this is a material container. If so, check if any material with the same GUID is being used by any
+        # check if this is a material container. If so, check if any material with the same base is being used by any
         # stacks.
         container_ids_to_check = [container_id]
         container_results = self._container_registry.findInstanceContainers(id = container_id, type = "material")
         if container_results:
             this_container = container_results[0]
-            container_guid = this_container.getMetaDataEntry("GUID")
-            # check all material container IDs with the same GUID
-            material_containers = self._container_registry.findInstanceContainers(id = container_id,
-                                                                                  GUID = container_guid,
+            material_base_file = this_container.getMetaDataEntry("base_file", this_container.getId())
+            # check all material container IDs with the same base
+            material_containers = self._container_registry.findInstanceContainers(base_file = material_base_file,
                                                                                   type = "material")
             if material_containers:
                 container_ids_to_check = [container.getId() for container in material_containers]