+magit/clone: fix void-function ghub--username

modules/tools/magit/autoload.el

@@ -98,6 +98,8 @@ control in buffers."
 + REPO: assumes {`+magit-default-clone-url'}/{USER}/REPO, where {USER} is
   ascertained from your global gitconfig."
   (interactive
+   (progn
+     (require 'ghub)
      (let* ((user (ghub--username (ghub--host)))
             (repo (read-from-minibuffer
                    "Clone repository (user/repo or url): "
@@ -108,9 +110,10 @@ control in buffers."
              (read-directory-name
               "Destination: "
               magit-clone-default-directory
-            name nil name))))
+              name nil name)))))
   (magit-clone
    (cond ((string-match-p "^[^/]+$" url-or-repo)
+          (require 'ghub)
           (format +magit-default-clone-url (ghub--username (ghub--host)) url-or-repo))
          ((string-match-p "^\\([^/]+\\)/\\([^/]+\\)/?$" url-or-repo)
           (apply #'format +magit-default-clone-url (split-string url-or-repo "/" t)))