Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  expand-file-name(nil)
  (let* ((cwd ...) (magit-dir ...)) (if magit-dir (file-name-as-directory ...) nil))
  magit-get-top-dir(nil)
  (let* ((topdir ...) (buf ...)) (switch-to-buffer buf) (magit-mode-init topdir (quote status) (function magit-refresh-status)))
  magit-status(nil)
  call-interactively(magit-status t nil)
  execute-extended-command(nil)
  call-interactively(execute-extended-command nil nil)