Fixed another issue

backend/Config.php

@@ -18,7 +18,7 @@ class Config {
     }
 
     public static function createFromGlobals() {
-        if (null !== db_connector)
+        if (defined(db_connector) && null !== db_connector)
             return new Config(path_prefix, db_connector, db_user, db_pass);
         else
             return new Config(path_prefix, 'pgsql:host=' . db_host . ';port=' . db_port . ';dbname=' . db_name . '', db_user, db_pass);