master 9000aea: Make sure to return some valid project root

[Dmitry Gutov]

branch: master
commit 9000aeaed446a02aaf0684e02f40312b3a2e0b59
Author: Dmitry Gutov <dgutov@yandex.ru>
Commit: Dmitry Gutov <dgutov@yandex.ru>

    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.
---
 lisp/progmodes/project.el | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index ba95ed0..d034443 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)))