*Completions* in minibuffer-only frames

[martin rudalics <rudalics@gmx.at>]

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With Emacs 26 and a minibuffer-only frame, *Completions* may be
displayed in the minibuffer window.  To reproduce with emacs -Q do
(make-frame '((minibuffer . only))) and in that minibuffer-only frame
type C-h f followed by TAB.  This will display *Completions* in the
minibuffer window and it can become quite complicated to get rid of it
again.  Hence I would like to apply the attached trivial patch to the
release branch.  Any objections?

Thanks, martin

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diff --git a/lisp/window.el b/lisp/window.el
index 4b30609..0a36ae7 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -7397,6 +7397,7 @@ display-buffer-below-selected
 	     (window--display-buffer
 	      buffer window 'window alist display-buffer-mark-dedicated))
 	(and (setq window (window-in-direction 'below))
+             (not (window-minibuffer-p window))
 	     (not (window-dedicated-p window))
 	     (window--display-buffer
 	      buffer window 'reuse alist display-buffer-mark-dedicated)))))
@@ -7432,6 +7433,7 @@ display-buffer-at-bottom
 	     (window--display-buffer
 	      buffer window 'window alist display-buffer-mark-dedicated))
 	(and (setq window bottom-window)
+             (not (window-minibuffer-p window))
 	     (not (window-dedicated-p window))
 	     (window--display-buffer
 	      buffer window 'reuse alist display-buffer-mark-dedicated)))))