Fix a longstanding issue with ellispsis on top of the window

* org.el (org-show-context): Remove useless catch.  Make sure the
top of the window is a visible headline.
* org.el (org-activate-plain-links): Remove unused catch.

* org-macs.el (org-get-alist-option): Return nil, not (nil), so
that `org-show-context' DTRT.

Thanks to Samuel Wales for his patience in reporting this.

lisp/org-macs.el

@@ -263,7 +263,7 @@ in `org-rm-props'."
   (cond ((eq key t) t)
 	((eq option t) t)
 	((assoc key option) (cdr (assoc key option)))
-	(t (cdr (assq 'default option)))))
+	(t (delq nil (cdr (assq 'default option))))))
 
 (defsubst org-check-external-command (cmd &optional use no-error)
   "Check if external program CMD for USE exists, error if not.

lisp/org.el

@@ -5303,21 +5303,20 @@ will be prompted for."
 
 (defun org-activate-plain-links (limit)
   "Run through the buffer and add overlays to links."
-  (catch 'exit
-    (let (f)
-      (when (and (re-search-forward (concat org-plain-link-re) limit t)
-		 (not (org-in-src-block-p)))
-	(org-remove-flyspell-overlays-in (match-beginning 0) (match-end 0))
-	(setq f (get-text-property (match-beginning 0) 'face))
-	(unless (or (org-in-src-block-p)
-		    (eq f 'org-tag)
-		    (and (listp f) (memq 'org-tag f)))
-	  (add-text-properties (match-beginning 0) (match-end 0)
-			       (list 'mouse-face 'highlight
-				     'face 'org-link
-				     'keymap org-mouse-map))
-	  (org-rear-nonsticky-at (match-end 0)))
-	t))))
+  (let (f)
+    (when (and (re-search-forward (concat org-plain-link-re) limit t)
+	       (not (org-in-src-block-p)))
+      (org-remove-flyspell-overlays-in (match-beginning 0) (match-end 0))
+      (setq f (get-text-property (match-beginning 0) 'face))
+      (unless (or (org-in-src-block-p)
+		  (eq f 'org-tag)
+		  (and (listp f) (memq 'org-tag f)))
+	(add-text-properties (match-beginning 0) (match-end 0)
+			     (list 'mouse-face 'highlight
+				   'face 'org-link
+				   'keymap org-mouse-map))
+	(org-rear-nonsticky-at (match-end 0)))
+      t)))
 
 (defun org-activate-code (limit)
   (if (re-search-forward "^[ \t]*\\(:\\(?: .*\\|$\\)\n?\\)" limit t)
@@ -12845,27 +12844,27 @@ How much context is shown depends upon the variables
 	(following-p (org-get-alist-option org-show-following-heading key))
 	(entry-p     (org-get-alist-option org-show-entry-below key))
 	(siblings-p  (org-get-alist-option org-show-siblings key)))
-    (catch 'exit
-      ;; Show heading or entry text
-      (if (and heading-p (not entry-p))
-	  (org-flag-heading nil)    ; only show the heading
-	(and (or entry-p (outline-invisible-p) (org-invisible-p2))
-	     (org-show-hidden-entry)))    ; show entire entry
-      (when following-p
-	;; Show next sibling, or heading below text
-	(save-excursion
-	  (and (if heading-p (org-goto-sibling) (outline-next-heading))
-	       (org-flag-heading nil))))
-      (when siblings-p (org-show-siblings))
-      (when hierarchy-p
-	;; show all higher headings, possibly with siblings
-	(save-excursion
-	  (while (and (condition-case nil
-			  (progn (org-up-heading-all 1) t)
-			(error nil))
-		      (not (bobp)))
-	    (org-flag-heading nil)
-	    (when siblings-p (org-show-siblings))))))))
+    ;; Show heading or entry text
+    (if (and heading-p (not entry-p))
+	(org-flag-heading nil)    ; only show the heading
+      (and (or entry-p (outline-invisible-p) (org-invisible-p2))
+	   (org-show-hidden-entry)))    ; show entire entry
+    (when following-p
+      ;; Show next sibling, or heading below text
+      (save-excursion
+	(and (if heading-p (org-goto-sibling) (outline-next-heading))
+	     (org-flag-heading nil))))
+    (when siblings-p (org-show-siblings))
+    (when hierarchy-p
+      ;; show all higher headings, possibly with siblings
+      (save-excursion
+	(while (and (condition-case nil
+			(progn (org-up-heading-all 1) t)
+		      (error nil))
+		    (not (bobp)))
+	  (org-flag-heading nil)
+	  (when siblings-p (org-show-siblings)))))
+    (save-excursion (goto-char (window-start)) (recenter 0))))
 
 (defvar org-reveal-start-hook nil
   "Hook run before revealing a location.")