Track down nils for cancellation w/ include?

lib/simplekit.rb

@@ -114,7 +114,7 @@ module SimpleKit
     def should_cancel?(event_notice)
       e = event_notice.event
       if @cancel_set.key? e
-        if @cancel_set[e] === nil
+        if @cancel_set[e].include? nil
           @cancel_set[e].delete nil
           @cancel_set.delete e if @cancel_set[e].empty?
           return true