lisp/ob-scheme.el: Do not hide Scheme evaluation errors

* lisp/ob-eval.el (org-babel-eval-error-notify): Handle an exit code of nil.

* lisp/ob-scheme.el (org-babel-expand-body:scheme)
(org-babel-scheme-get-repl, org-babel-scheme-make-session-name)
(org-babel-scheme-execute-with-geiser)
(org-babel-scheme--table-or-string, org-babel-execute:scheme):
Display Scheme evaluation errors in an error buffer using
`org-babel-eval-error-notify'.

TINYCHANGE

lisp/ob-eval.el

@@ -37,16 +37,21 @@
 (declare-function org-babel-temp-file "ob-core" (prefix &optional suffix))
 
 (defun org-babel-eval-error-notify (exit-code stderr)
-  "Open a buffer to display STDERR and a message with the value of EXIT-CODE."
+  "Open a buffer to display STDERR and a message with the value of EXIT-CODE.
+If EXIT-CODE is nil, display the message without a code."
   (let ((buf (get-buffer-create org-babel-error-buffer-name)))
     (with-current-buffer buf
       (goto-char (point-max))
       (save-excursion
         (unless (bolp) (insert "\n"))
         (insert stderr)
-        (insert (format "[ Babel evaluation exited with code %S ]" exit-code))))
+        (if exit-code
+            (insert (format "[ Babel evaluation exited with code %S ]" exit-code))
+          (insert "[ Babel evaluation exited abnormally ]"))))
     (display-buffer buf))
-  (message "Babel evaluation exited with code %S" exit-code))
+  (if exit-code
+      (message "Babel evaluation exited with code %S" exit-code)
+    (message "Babel evaluation exited abnormally")))
 
 (defun org-babel-eval (command query)
   "Run COMMAND on QUERY.

lisp/ob-scheme.el

@@ -65,6 +65,8 @@
 (declare-function geiser-repl-exit "ext:geiser-repl" (&optional arg))
 (declare-function geiser-eval--retort-output "ext:geiser-eval" (ret))
 (declare-function geiser-eval--retort-result-str "ext:geiser-eval" (ret prefix))
+(declare-function geiser-eval--retort-error "ext:geiser-eval" (ret))
+(declare-function geiser-eval--retort-error-msg "ext:geiser-eval" (err))
 
 (defcustom org-babel-scheme-null-to 'hline
   "Replace `null' and empty lists in scheme tables with this before returning."
@@ -193,22 +195,30 @@ is true; otherwise returns the last value."
                                   #'geiser-eval-region)
                                 (point-min)
                                 (point-max))))
-	      (setq result (if output
+	      (let ((err (geiser-eval--retort-error ret)))
+		(setq result (cond
+			      (output
 			       (or (geiser-eval--retort-output ret)
-				   "Geiser Interpreter produced no output")
-			     (geiser-eval--retort-result-str ret "")))))
+				   "Geiser Interpreter produced no output"))
+			      (err nil)
+			      (t (geiser-eval--retort-result-str ret ""))))
 	  (when (not repl)
 	    (save-current-buffer (set-buffer repl-buffer)
 				 (geiser-repl-exit))
 	    (set-process-query-on-exit-flag (get-buffer-process repl-buffer) nil)
-	    (kill-buffer repl-buffer)))))
+		  (kill-buffer repl-buffer))
+		(when err
+		  (let ((msg (geiser-eval--error-msg err)))
+		    (org-babel-eval-error-notify
+		     nil
+		     (concat (if (listp msg) (car msg) msg) "\n"))))))))))
     result))
 
 (defun org-babel-scheme--table-or-string (results)
   "Convert RESULTS into an appropriate elisp value.
 If the results look like a list or tuple, then convert them into an
 Emacs-lisp table, otherwise return the results as a string."
-  (let ((res (org-babel-script-escape results)))
+  (let ((res (and results (org-babel-script-escape results))))
     (cond ((listp res)
            (mapcar (lambda (el)
 		     (if (or (null el) (eq el 'null))