Fix error when not in any project.

Go to default inbox when in no project

projectorg.el

@@ -47,17 +47,20 @@ Contains the general notes files, the projects list files and each project notes
   "Return the full project name.
 
 It is the result of substracting the projectorg-projects-root string from the beginning of the path of the project, as returned by projectile-project-p."
-  (let ((project-path (projectile-project-p)))
-    (and
-     (string= (substring project-path 0 (length projectorg-projects-root))
-              projectorg-projects-root)
-     (substring project-path (length projectorg-projects-root) -1))))
+  (when (projectile-project-p)
+    (let ((project-path (projectile-project-p)))
+      (and
+       (string= (substring project-path 0 (length projectorg-projects-root))
+                projectorg-projects-root)
+       (substring project-path (length projectorg-projects-root) -1)))))
 
 (defun projectorg/notes-file ()
   "Returns the notes-file location.
 
 It is an org file, with the same name as the project (including subdirectories), located in the *org* directory in projectorg-projects-root."
-  (concat projectorg-projects-root "org/" (projectorg/project-name) ".org"))
+  (let ((project-name (projectorg/project-name)))
+    (when project-name
+      (concat projectorg-projects-root "org/" project-name ".org"))))
 
 (defun projectorg/go-to-inbox ()
   "Go to org-default-notes-file."