fix bug preventing the installation of locomotive as an engine

doc/TODO

@@ -1,9 +1,10 @@
 BOARD:
 
-- bugs:
-  - #50
-  - #51
+x bugs:
+  x #50
+  x #51
 ~ editable_elements: inheritable: false (Mattias) => seems to be fixed by Dirk's last pull request (#44) => content tag
+- upgrade warning if new version of locomotive (maybe based on the commit id)
 - duostack version
 - 2 different sites on the same main domain (one in www, the other one in something else) (Raphael Costa)
 - seo section for the page form: seo title, seo keywords, seo description

lib/locomotive.rb

@@ -58,8 +58,12 @@ module Locomotive
     Devise.mailer_sender = self.config.mailer_sender
 
     # Load all the dynamic classes (custom fields)
+    begin
       ContentType.all.collect(&:fetch_content_klass)
       AssetCollection.all.collect(&:fetch_asset_klass)
+    rescue ::Mongoid::Errors::InvalidDatabase => e
+      # let assume it's because of the first install (meaning no config.yml file)
+    end
   end
 
   def self.logger(message)