Revert "org.el: (org-mode): Use `face-background' instead of `org-find-invisible-foreground'"

This reverts commit 4549f0c99cef65c68879641d2a96ad486b64e6b1.

lisp/org.el

@@ -5134,7 +5134,7 @@ The following commands are available:
     (unless org-inhibit-startup-visibility-stuff
       (org-set-startup-visibility)))
   ;; Try to set org-hide correctly
-  (set-face-foreground 'org-hide (face-background 'default nil 'default)))
+  (set-face-foreground 'org-hide (org-find-invisible-foreground)))
 
 (when (fboundp 'abbrev-table-put)
   (abbrev-table-put org-mode-abbrev-table
@@ -5142,6 +5142,21 @@ The following commands are available:
 
 (put 'org-mode 'flyspell-mode-predicate 'org-mode-flyspell-verify)
 
+
+(defun org-find-invisible-foreground ()
+  (let ((candidates (remove
+		     "unspecified-bg"
+		     (nconc
+		      (list (face-background 'default)
+			    (face-background 'org-default))
+		      (mapcar
+		       (lambda (alist)
+			 (when (boundp alist)
+			   (cdr (assoc 'background-color (symbol-value alist)))))
+		       '(default-frame-alist initial-frame-alist window-system-default-frame-alist))
+		      (list (face-foreground 'org-hide))))))
+    (car (remove nil candidates))))
+
 (defun org-current-time ()
   "Current time, possibly rounded to `org-time-stamp-rounding-minutes'."
   (if (> (car org-time-stamp-rounding-minutes) 1)