Don't die when trying to dup a singleton unfrozen object

lib/rackstash/message.rb

@@ -83,7 +83,11 @@ module Rackstash
     end
 
     def dup_freeze(obj)
-      obj.frozen? ? obj : obj.dup.freeze
+      if obj.frozen?
+        obj
+      else
+        obj.dup.freeze rescue obj
+      end
     end
   end
 end

spec/rackstash/message_spec.rb

@@ -26,6 +26,16 @@ describe Rackstash::Message do
 
       expect(message.message).to eq exception
     end
+
+    it 'attempts to dup non-frozen objects' do
+      rational = Rational(2, 3)
+      expect(rational).to_not be_frozen
+
+      message = Rackstash::Message.new(rational)
+
+      expect(message.message).to_not be_frozen
+      expect(message.message).to equal rational
+    end
   end
 
   describe '#severity' do