bug#71386: 29.1; Frame is auto-deleted even when it has multiple tabs

[martin rudalics via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

 > It would be great if the fix is done entirely in `window-deletable-p`,
 > but is the idea functions in `window-deletable-functions` could have
 > side-effects even though they are called from a predicate?

No.  We could emphasize that in the doc-string.  The idea is that such a
function can have 'window-deletable-p' return nil instead of 'frame' or
t.  WOW all functions on 'window-deletable-functions' have to agree that
'window-deletable-p' may return any non-nil value it initially proposes.

 > For tabs, I believe an ideal fix would close the tab in lieu of
 > deleting the frame when the buffer of a dedicated window is killed
 > (similar to what Juri does in per patches).

The patch I proposed will simply cause another buffer to be shown in
that window.  How this affects the tab bar code is beyond the limits of
'quit-restore-window' and colleagues.  I suppose the tab bar code should
do whatever it does when 'switch-to-prev-buffer' gets called.

martin