MessageVerifier raises an appropriate exception if the secret is nil

Otherwise this will lead to another error later on 
when generating a signature:
TypeError (no implicit conversion of nil into String).

1 files changed, 1 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/message_verifier.rb b/activesupport/lib/active_support/message_verifier.rb
index 8e6e1dcfeb..41e2e5a88f 100644
--- a/activesupport/lib/active_support/message_verifier.rb
+++ b/activesupport/lib/active_support/message_verifier.rb
@@ -27,6 +27,7 @@ module ActiveSupport
     class InvalidSignature < StandardError; end
 
     def initialize(secret, options = {})
+      raise ArgumentError, 'Secret should not be nil.' if secret.nil?
       @secret = secret
       @digest = options[:digest] || 'SHA1'
       @serializer = options[:serializer] || Marshal