Fix material container removal

CURA-6237

cura/Machines/MaterialManager.py

@@ -537,6 +537,24 @@ class MaterialManager(QObject):
             return
 
         nodes_to_remove = [material_group.root_material_node] + material_group.derived_material_node_list
+        # FIXME: CURA-6237
+        # Sort all nodes with respect to the container ID lengths in the ascending order so the base material container
+        # will be the last one to remove. Adding this is because in ContainerRegistry.removeContainer(), the container
+        # will be loaded if it has not been loaded before. If the base material has been removed before this happens,
+        # it will not be able to find and load the material container, resulting in a crash.
+        # We may need to consider changing how the signal ContainerRegistry.containerRemoved works: Now it requires
+        # the container that's being removed, meaning that in order to remove a container, it must be loaded first.
+        # But it can also be that for ContainerRegistry.containerRemoved, we just need to notify the id, name, and/or
+        # type of the container that's being removed, thus removing removeContainer()'s dependency on a container being
+        # loaded first.
+        nodes_to_remove = sorted(nodes_to_remove, key = lambda x: len(x.getMetaDataEntry("id", "")), reverse = True)
+        # Try to load all containers first. If there is any faulty ones, they will be put into the faulty container
+        # list, so removeContainer() can ignore those ones.
+        for node in nodes_to_remove:
+            container_id = node.getMetaDataEntry("id", "")
+            results = self._container_registry.findContainers(id = container_id)
+            if not results:
+                self._container_registry.addWrongContainerId(container_id)
         for node in nodes_to_remove:
             self._container_registry.removeContainer(node.getMetaDataEntry("id", ""))