diff --git a/cura/CuraApplication.py b/cura/CuraApplication.py
index 9d6a2361a1..e6fa00869a 100755
--- a/cura/CuraApplication.py
+++ b/cura/CuraApplication.py
@@ -682,7 +682,7 @@ class CuraApplication(QtApplication):
 
         Logger.log("i", "Initializing quality manager")
         from cura.Machines.QualityManager import QualityManager
-        self._quality_manager = QualityManager(container_registry, parent = self)
+        self._quality_manager = QualityManager(self, parent = self)
         self._quality_manager.initialize()
 
         Logger.log("i", "Initializing machine manager")
diff --git a/cura/Machines/QualityManager.py b/cura/Machines/QualityManager.py
index d924f4c83e..ce19624c21 100644
--- a/cura/Machines/QualityManager.py
+++ b/cura/Machines/QualityManager.py
@@ -5,8 +5,6 @@ from typing import TYPE_CHECKING, Optional, cast, Dict, List
 
 from PyQt5.QtCore import QObject, QTimer, pyqtSignal, pyqtSlot
 
-from UM.Application import Application
-
 from UM.ConfigurationErrorMessage import ConfigurationErrorMessage
 from UM.Logger import Logger
 from UM.Util import parseBool
@@ -22,7 +20,6 @@ if TYPE_CHECKING:
     from cura.Settings.GlobalStack import GlobalStack
     from .QualityChangesGroup import QualityChangesGroup
     from cura.CuraApplication import CuraApplication
-    from UM.Settings.ContainerRegistry import ContainerRegistry
 
 
 #
@@ -39,12 +36,11 @@ class QualityManager(QObject):
 
     qualitiesUpdated = pyqtSignal()
 
-    def __init__(self, container_registry: "ContainerRegistry", parent = None) -> None:
+    def __init__(self, application: "CuraApplication", parent = None) -> None:
         super().__init__(parent)
-        from cura.CuraApplication import CuraApplication
-        self._application = CuraApplication.getInstance()  # type: CuraApplication
+        self._application = application
         self._material_manager = self._application.getMaterialManager()
-        self._container_registry = container_registry
+        self._container_registry = self._application.getContainerRegistry()
 
         self._empty_quality_container = self._application.empty_quality_container
         self._empty_quality_changes_container = self._application.empty_quality_changes_container
@@ -460,7 +456,7 @@ class QualityManager(QObject):
     #   stack and clear the user settings.
     @pyqtSlot(str)
     def createQualityChanges(self, base_name: str) -> None:
-        machine_manager = CuraApplication.getInstance().getMachineManager()
+        machine_manager = self._application.getMachineManager()
 
         global_stack = machine_manager.activeMachine
         if not global_stack:
diff --git a/cura/OAuth2/AuthorizationHelpers.py b/cura/OAuth2/AuthorizationHelpers.py
index 6cb53d2252..f75ad9c9f9 100644
--- a/cura/OAuth2/AuthorizationHelpers.py
+++ b/cura/OAuth2/AuthorizationHelpers.py
@@ -4,7 +4,7 @@ import json
 import random
 from hashlib import sha512
 from base64 import b64encode
-from typing import Optional
+from typing import Dict, Optional
 
 import requests
 
@@ -28,33 +28,35 @@ class AuthorizationHelpers:
     #   \param authorization_code: The authorization code from the 1st step.
     #   \param verification_code: The verification code needed for the PKCE extension.
     #   \return: An AuthenticationResponse object.
-    def getAccessTokenUsingAuthorizationCode(self, authorization_code: str, verification_code: str)-> "AuthenticationResponse":
-        return self.parseTokenResponse(requests.post(self._token_url, data={
-            "client_id": self._settings.CLIENT_ID,
-            "redirect_uri": self._settings.CALLBACK_URL,
+    def getAccessTokenUsingAuthorizationCode(self, authorization_code: str, verification_code: str) -> "AuthenticationResponse":
+        data = {
+            "client_id": self._settings.CLIENT_ID if self._settings.CLIENT_ID is not None else "",
+            "redirect_uri": self._settings.CALLBACK_URL if self._settings.CALLBACK_URL is not None else "",
             "grant_type": "authorization_code",
             "code": authorization_code,
             "code_verifier": verification_code,
-            "scope": self._settings.CLIENT_SCOPES
-        }))  # type: ignore
+            "scope": self._settings.CLIENT_SCOPES if self._settings.CLIENT_SCOPES is not None else "",
+            }
+        return self.parseTokenResponse(requests.post(self._token_url, data = data))  # type: ignore
 
     #   Request the access token from the authorization server using a refresh token.
     #   \param refresh_token:
     #   \return: An AuthenticationResponse object.
-    def getAccessTokenUsingRefreshToken(self, refresh_token: str) -> AuthenticationResponse:
-        return self.parseTokenResponse(requests.post(self._token_url, data={
-            "client_id": self._settings.CLIENT_ID,
-            "redirect_uri": self._settings.CALLBACK_URL,
+    def getAccessTokenUsingRefreshToken(self, refresh_token: str) -> "AuthenticationResponse":
+        data = {
+            "client_id": self._settings.CLIENT_ID if self._settings.CLIENT_ID is not None else "",
+            "redirect_uri": self._settings.CALLBACK_URL if self._settings.CALLBACK_URL is not None else "",
             "grant_type": "refresh_token",
             "refresh_token": refresh_token,
-            "scope": self._settings.CLIENT_SCOPES
-        }))  # type: ignore
+            "scope": self._settings.CLIENT_SCOPES if self._settings.CLIENT_SCOPES is not None else "",
+        }
+        return self.parseTokenResponse(requests.post(self._token_url, data = data))  # type: ignore
 
     @staticmethod
     #   Parse the token response from the authorization server into an AuthenticationResponse object.
     #   \param token_response: The JSON string data response from the authorization server.
     #   \return: An AuthenticationResponse object.
-    def parseTokenResponse(token_response: requests.models.Response) -> AuthenticationResponse:
+    def parseTokenResponse(token_response: requests.models.Response) -> "AuthenticationResponse":
         token_data = None
 
         try:
diff --git a/cura/Scene/ConvexHullDecorator.py b/cura/Scene/ConvexHullDecorator.py
index 8532f40890..bdb4cbcba8 100644
--- a/cura/Scene/ConvexHullDecorator.py
+++ b/cura/Scene/ConvexHullDecorator.py
@@ -9,7 +9,6 @@ from UM.Math.Polygon import Polygon
 from UM.Scene.SceneNodeDecorator import SceneNodeDecorator
 from UM.Settings.ContainerRegistry import ContainerRegistry
 
-
 from cura.Settings.ExtruderManager import ExtruderManager
 from cura.Scene import ConvexHullNode