Make sure to return some valid project root

* lisp/progmodes/project.el (project-prompt-project-dir):
If the user just pressed RET on prompt, prompt again.

1 files changed, 4 insertions, 1 deletions

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index ba95ed094ed..d034443907d 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1308,7 +1308,10 @@ It's also possible to enter an arbitrary directory not in the list."
           ;; completion style).
           (project--file-completion-table
            (append project--list `(,dir-choice))))
-         (pr-dir (completing-read "Select project: " choices nil t)))
+         (pr-dir ""))
+    (while (equal pr-dir "")
+      ;; If the user simply pressed RET, do this again until they don't.
+      (setq pr-dir (completing-read "Select project: " choices nil t)))
     (if (equal pr-dir dir-choice)
         (read-directory-name "Select directory: " default-directory nil t)
       pr-dir)))