bug#47300: delete-window to select window with same position

[Juri Linkov]

>> No.  You probably have to save the old position of the deleted window's
>> point in frame coordinates and have the function that selects the new
>> window use the window that is now at that frame position.
>
> Just to explain what I meant above look at the attached patch.  I think
> we should then move the `get-mru-window' call to `delete-window' too and
> combine them all with the 'no-other-window' check so we never select a
> window with NORECORD nil twice here.
>
> [2. text/x-patch; window.el.diff]...

I don't know why, but sometimes `window-at' returns 'nil'.