Construct sources on the fly.

Allows people to change `helm-dictionary-database` without having to
restart Emacs.

helm-dictionary.el

@@ -248,13 +248,6 @@ browser in `helm-browse-url-default-browser-alist'"
               ("Insert target language term" . helm-dictionary-insert-l2term))))
 
 
-(defvar helm-source-dictionary
-  (mapcar
-   (lambda (x) (helm-dictionary-build (car x) (cdr x)))
-   (if (stringp helm-dictionary-database)
-       (list (cons "Search dictionary" helm-dictionary-database))
-     helm-dictionary-database)))
-
 (defvar helm-source-dictionary-online
   (helm-build-sync-source "Look up online"
     :match (lambda (_candidate) t)
@@ -271,10 +264,16 @@ browser in `helm-browse-url-default-browser-alist'"
 ;;;###autoload
 (defun helm-dictionary ()
   (interactive)
-  (helm :sources (append helm-source-dictionary (list helm-source-dictionary-online))
-        :full-frame t
-        :candidate-number-limit 500
-        :buffer "*helm dictionary*"))
+  (let ((helm-source-dictionary
+         (mapcar
+          (lambda (x) (helm-dictionary-build (car x) (cdr x)))
+          (if (stringp helm-dictionary-database)
+              (list (cons "Search dictionary" helm-dictionary-database))
+            helm-dictionary-database))))
+    (helm :sources (append helm-source-dictionary (list helm-source-dictionary-online))
+          :full-frame t
+          :candidate-number-limit 500
+          :buffer "*helm dictionary*")))
 
 (provide 'helm-dictionary)