Disable upgrading current settings altogether

The current settings in 2.1 specified a machine instance. In 2.2 they specify a machine definition. There is not enough information in one file to be able to translate that.

Contributes to issue CURA-844.

plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py

@@ -91,12 +91,9 @@ class MachineInstance:
 
         if has_machine_qualities: #This machine now has machine-quality profiles.
             active_material += "_" + variant_materials #That means that the profile was split into multiple.
-            current_settings = "" #The profile didn't know the definition ID when it was upgraded, so it will have been invalid. Sorry, your current settings are lost now.
-        else:
-            current_settings = self._name + "_current_settings"
 
         containers = [
-            current_settings,
+            "", #The current profile doesn't know the definition ID when it was upgraded, only the instance ID, so it will be invalid. Sorry, your current settings are lost now.
             active_quality_changes,
             active_quality,
             active_material,

plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py

@@ -80,7 +80,7 @@ class Profile:
         import VersionUpgrade21to22 # Import here to prevent circular dependencies.
 
         if self._name == "Current settings":
-            self._filename += "_current_settings" #This resolves a duplicate ID arising from how Cura 2.1 stores its current settings.
+            return None #Can't upgrade these, because the new current profile needs to specify the definition ID and the old file only had the machine instance, not the definition.
 
         config = configparser.ConfigParser(interpolation = None)