Reverse treatment of universal argument for helm shortcut menu

Usually, when searching for important documents vie `db/helm-shortcuts`, I
forget to include the universal argument, abort the current search and repeat
it.  This is annoying.  Since listing documents is fast enough, including them
by default should alleviate this issue.

When retrieving the list of documents is too slow and should be disabled
interactively, providing a universal argument excludes this listing now.

init.el

@@ -2356,10 +2356,15 @@ The password is assumed to be stored at the PASSWORD property."
 
 (defun db/helm-shortcuts (arg)
   "Open helm completion on common locations.
-With given ARG, display files in `db/important-document-path’."
-  (interactive "p")
-  (require 'helm-bookmark)
-  (require 'helm-for-files)             ; for helm-source-recentf
+
+With universal argument ARG, inhibit display of files in
+`db/important-document-path’.  This might be helpful when loading
+is too slow (in this case, `db/important-document-path' should
+eventuelly be set to nil, however)."
+  (interactive "P")
+  (eval-when-compile
+    (require 'helm-bookmark)
+    (require 'helm-for-files))          ; for helm-source-recentf
   (helm :sources (list
                   (helm-make-source "Frequently Used" 'helm-source-sync
                     :candidates (mapcar #'(lambda (entry)
@@ -2376,7 +2381,7 @@ With given ARG, display files in `db/important-document-path’."
 
                   ;; if prefix arg is given, extract files from
                   ;; `db/important-documents-path’ and list them as well
-                  (when (and (= arg 4)
+                  (when (and (not arg)
                              (file-directory-p db/important-documents-path))
                     (let ((search-path (expand-file-name db/important-documents-path)))
                       (helm-make-source "Important files" 'helm-source-sync