Cover the last remaining case when setting the print sequence

If for some reason the print sequence is set to one-at-a-time be default in the printer definition
and the number of extruders of the printer is set to >=2, then the print_sequence won't show up in
neither the quality changes nor the user changes, yet it will still have "one-at-a-time" as a
value. In a such case, it will still need to be set to "all-at-once" in the user changes.

This is a theoretical case, as it is very unlikely for a printer to have "one-at-a-time" set by
default in its definition (.def.json) file and still be able to support more than one extruders.
But it is a world full of possibilities out there, so you never know...

CURA-7827

cura/Settings/MachineManager.py

@@ -877,19 +877,21 @@ class MachineManager(QObject):
 
         user_changes_container = self._global_container_stack.userChanges
         quality_changes_container = self._global_container_stack.qualityChanges
-        print_sequence_in_quality_changes = quality_changes_container.getProperty(setting_key, "value")
-        print_sequence_in_user_changes = user_changes_container.getProperty(setting_key, "value")
+        print_sequence_quality_changes = quality_changes_container.getProperty(setting_key, "value")
+        print_sequence_user_changes = user_changes_container.getProperty(setting_key, "value")
 
-        # If the quality changes has the wrong value, then set the correct value in the user changes
-        if print_sequence_in_quality_changes and print_sequence_in_quality_changes != new_value:
-            user_changes_container.setProperty(setting_key, "value", new_value)
-            Logger.log("d", "Setting '{}' in '{}' to '{}' because there are more than 1 enabled extruders.".format(setting_key, user_changes_container, new_value))
-        # If the quality changes has no value or the correct value and the user changes container has the wrong value,
-        # then reset the setting in the user changes (so that the circular revert-changes arrow will now show up in the
-        # interface)
-        elif print_sequence_in_user_changes and print_sequence_in_user_changes != new_value:
+        # If the user changes container has a value and its the incorrect value, then reset the setting in the user
+        # changes (so that the circular revert-changes arrow will now show up in the interface)
+        if print_sequence_user_changes and print_sequence_user_changes != new_value:
             user_changes_container.removeInstance(setting_key)
             Logger.log("d", "Resetting '{}' in container '{}' because there are more than 1 enabled extruders.".format(setting_key, user_changes_container))
+        # If the print sequence doesn't exist in either the user changes or the quality changes (yet it still has the
+        # wrong value in the global stack), or it exists in the quality changes and it has the wrong value, then set it
+        # in the user changes
+        elif (not print_sequence_quality_changes and not print_sequence_user_changes) \
+                or (print_sequence_quality_changes and print_sequence_quality_changes != new_value):
+            user_changes_container.setProperty(setting_key, "value", new_value)
+            Logger.log("d", "Setting '{}' in '{}' to '{}' because there are more than 1 enabled extruders.".format(setting_key, user_changes_container, new_value))
 
     def setActiveMachineExtruderCount(self, extruder_count: int) -> None:
         """Set the amount of extruders on the active machine (global stack)