QMainWindow::restoreState() changes orientation of dock widgets which have not been there when the state was saved

A main window containing dock widgets can store the state and restore it next time with the same widgets.
But if there are new dock widgets available compared to when the state was stored their orientation is overwritten by QMainWindow::restoreState().

I create a minimal example which shows the issue.
The following steps will reproduce the issue:

• build the application (e.g. using CMake)
• start application
• click "add horizontal"
• click "add horizontal"
• click "add vertical"
• click "add horizontal"
  ... the layout will look like this:
  11 22 44
  33333 44
• click "save state"
• close application

• start application
• click "add vertical" 5 times
  ... the layout will look like this:
  11
  22
  33
  44
  55
• click "restore state"
  ... the layout will look like this:
  11 22 44 55
  33333 44 55

BUT since 5 was not known before I would expect its orientation
(vertical) to not change by the restoreState invocation
... the layout should look like this:
11 22 44
33333 44
55555555