Fix a nil error when alternative public key isn't present

Author: Ben Lavender

lib/chatops/controller.rb

@@ -167,6 +167,7 @@ def should_authenticate_chatops?
     end
 
     def signature_valid?(key_string, signature, signature_string)
+      return false unless key_string.present?
       digest = OpenSSL::Digest::SHA256.new
       decoded_signature = Base64.decode64(signature)
       public_key = OpenSSL::PKey::RSA.new(key_string)

lib/chatops/controller/version.rb

@@ -1,3 +1,3 @@
 module ChatopsController
-  VERSION = "3.0.0"
+  VERSION = "3.0.1"
 end