No longer create the machine manager twice

cura/CuraApplication.py

@@ -762,7 +762,7 @@ class CuraApplication(QtApplication):
 
         Logger.log("i", "Initializing machine manager")
         self._setLoadingHint(self._i18n_catalog.i18nc("@info:progress", "Initializing machine manager..."))
-        self._machine_manager = MachineManager(self, parent = self)
+        self.getMachineManager()
         self.processEvents()
 
         Logger.log("i", "Initializing container manager")
@@ -935,7 +935,7 @@ class CuraApplication(QtApplication):
 
     def getMachineManager(self, *args) -> MachineManager:
         if self._machine_manager is None:
-            self._machine_manager = MachineManager(self)
+            self._machine_manager = MachineManager(self, parent = self)
         return self._machine_manager
 
     def getExtruderManager(self, *args) -> ExtruderManager: