Where is Null pointer?

I have a Null Pointer

I check all my variable at my code

I can't find a possible Null pointer
I know It come from ExternalMessage Class

It said like below

msg = new ExternalMessage();
msg.sendMessage(sender,receiver,subject,content)

Finally I got the idea
This sendMessage have addMessage method call inside.

The problem is the Exception wrapper

It hide the real problem

Rake on Ubuntu

I try to install the spree, when I try to do "rake db:bootstrap", it gave me error like this,

rake aborted!
undefined method `reenable' for [environment]>:Rake::Task

It turn out I install Ubuntu's rake, after I uninstall the rake of ubuntu, it work fine.