bug#53662: 29.0.50; Cannot use tab-new from side window

[Juri Linkov]

> If you attempt to tab-bar-new-tab while in a side window you get:
>
> split-window: Cannot split side window or parent of side window
>
> It also deletes other windows and leaves you in a very awkward
> side-window-only state.
>
> To repro:
>
> emacs -Q
> M-x tab-bar-mode
> M-: (display-buffer-in-side-window (get-buffer "*Messages*") '((side . 
> bottom)))
> C-x o
> M-x tab-new

Thanks for the bug report.

Martin, could you suggest how to ignore window-sideness
while splitting the side window?  'tab-bar-new-tab-to'
currently uses such trick to create a new window:

      (let ((ignore-window-parameters t))
        (delete-other-windows))
      (unless (eq tab-bar-new-tab-choice 'window)
        ;; Create a new window to get rid of old window parameters
        ;; (e.g. prev/next buffers) of old window.
        (split-window) (delete-window))

but this fails in side windows.