apropos-library: Check for null library in load-history

[Daniel Jensen]

apropos-library does not handle a null library name in load-history
correctly. This patch fixes the problem.

--- emacs/lisp/apropos.el       2009-01-05 04:18:41.000000000 +0100
+++ emacs-mod/lisp/apropos.el   2009-02-11 22:58:19.000000000 +0100
@@ -573,11 +573,12 @@
           (nconc (delq nil
                        (mapcar
                         (lambda (l)
-                          (setq l (file-name-nondirectory l))
-                          (while
-                              (not (equal (setq l (file-name-sans-extension l))
-                                          l)))
-                          l)
+                          (when (stringp l)
+                            (setq l (file-name-nondirectory l))
+                            (while
+                                (not (equal (setq l (file-name-sans-extension 
l))
+                                            l)))
+                            l))
                         (mapcar 'car load-history)))
                  (mapcar 'car load-history))))
      (list (completing-read "Describe library: " libs nil t))))