Fix M-x package-install failure if no archive has been fetched yet.

* emacs-lisp/package.el (package-install): Run
package-refresh-contents if there is no archive yet.

Fixes: debbugs:97978

lisp/ChangeLog

+2012-01-28  Phil Hagelberg  <phil@hagelb.org>
+
+	* emacs-lisp/package.el (package-install): Run
+	package-refresh-contents if there is no archive yet (Bug#97978).
+
 2012-01-28  Chong Yidong  <cyd@gnu.org>
 
 	* emacs-lisp/package.el (package-maybe-load-descriptor): New

lisp/emacs-lisp/package.el

@@ -889,6 +889,8 @@ archive in `package-archives'.  Interactively, prompt for NAME."
      ;; symbols for completion.
      (unless package--initialized
        (package-initialize t))
+     (unless package-archive-contents
+       (package-refresh-contents))
      (list (intern (completing-read
 		    "Install package: "
 		    (mapcar (lambda (elt)