bug#37733: [PATCH]: Erroneous grep call thows exception in compilation-tear-down-arrow-spec-in-margin.

[Alan Mackenzie]

In master:
emacs -Q
C-u M-x grep <CR>
grep --color -nH --null '-syn-' *.el <CR> ; Note the '-syn-' is
                                  ; interpreted by grep as flags.

This throws an exception.

Fix as follows:


diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index e312def18d..25c8a4d067 100644
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -2669,10 +2669,11 @@ compilation-set-up-arrow-spec-in-margin
 
 (defun compilation-tear-down-arrow-spec-in-margin ()
   "Restore compilation-arrow-overlay to not using the margin, which is 
removed."
-  (overlay-put compilation-arrow-overlay 'before-string nil)
-  (delete-overlay compilation-arrow-overlay)
-  (setq compilation-arrow-overlay nil)
-  (set-window-margins (selected-window) (- (car (window-margins)) 2)))
+  (when (overlayp compilation-arrow-overlay)
+    (overlay-put compilation-arrow-overlay 'before-string nil)
+    (delete-overlay compilation-arrow-overlay)
+    (setq compilation-arrow-overlay nil)
+    (set-window-margins (selected-window) (- (car (window-margins)) 2))))
 
 (defun compilation-set-overlay-arrow (w)
   "Set up, or switch off, the overlay-arrow for window W."

.

-- 
Alan Mackenzie (Nuremberg, Germany).