Fix import issues

CURA-6600

cura/Machines/MachineNode.py

@@ -3,6 +3,7 @@
 
 from typing import TYPE_CHECKING
 
+from UM.Logger import Logger
 from UM.Util import parseBool
 from UM.Settings.ContainerRegistry import ContainerRegistry  # To find all the variants for this machine.
 from UM.Settings.Interfaces import ContainerInterface
@@ -22,8 +23,11 @@ class MachineNode(ContainerNode):
         self.variants = {}  # type: Dict[str, VariantNode] # Mapping variant names to their nodes.
         self.global_qualities = {}  # type: Dict[str, QualityNode] # Mapping quality types to the global quality for those types.
         container_registry = ContainerRegistry.getInstance()
-
-        my_metadata = container_registry.findContainersMetadata(id = container_id)[0]
+        try:
+            my_metadata = container_registry.findContainersMetadata(id = container_id)[0]
+        except IndexError:
+            Logger.log("Unable to find metadata for container %s", container_id)
+            my_metadata = {}
         # Some of the metadata is cached upon construction here.
         # ONLY DO THAT FOR METADATA THAT DOESN'T CHANGE DURING RUNTIME!
         # Otherwise you need to keep it up-to-date during runtime.

cura/Settings/ContainerManager.py

@@ -28,7 +28,6 @@ if TYPE_CHECKING:
     from cura.Machines.ContainerNode import ContainerNode
     from cura.Machines.MaterialNode import MaterialNode
     from cura.Machines.QualityChangesGroup import QualityChangesGroup
-    from cura.Settings.MachineManager import MachineManager
     from cura.Machines.MaterialManager import MaterialManager
     from cura.Machines.QualityManager import QualityManager
 
@@ -269,11 +268,11 @@ class ContainerManager(QObject):
     #   \return \type{bool} True if successful, False if not.
     @pyqtSlot(result = bool)
     def updateQualityChanges(self) -> bool:
-        global_stack = MachineManager.getInstance().activeMachine
+        global_stack = cura.CuraApplication.CuraApplication.getInstance().getMachineManager().activeMachine
         if not global_stack:
             return False
 
-        MachineManager.getInstance().blurSettings.emit()
+        cura.CuraApplication.CuraApplication.getInstance().getMachineManager().blurSettings.emit()
 
         current_quality_changes_name = global_stack.qualityChanges.getName()
         current_quality_type = global_stack.quality.getMetaDataEntry("quality_type")
@@ -296,14 +295,14 @@ class ContainerManager(QObject):
 
             self._performMerge(quality_changes, stack.getTop())
 
-        MachineManager.getInstance().activeQualityChangesGroupChanged.emit()
+        cura.CuraApplication.CuraApplication.getInstance().getMachineManager().activeQualityChangesGroupChanged.emit()
 
         return True
 
     ##  Clear the top-most (user) containers of the active stacks.
     @pyqtSlot()
     def clearUserContainers(self) -> None:
-        machine_manager = MachineManager.getInstance()
+        machine_manager = cura.CuraApplication.CuraApplication.getInstance().getMachineManager()
         machine_manager.blurSettings.emit()
 
         send_emits_containers = []