Fix flaky adhoc bad-hacking generator code

Author: amatsuda

lib/generators/stateful_enum/plantuml_generator.rb

@@ -46,7 +46,7 @@ def event(name, &block)
 
     class EventStore < ::StatefulEnum::Machine::Event
       def initialize(items, states, prefix, suffix, name, &block)
-        @items, @states, @prefix, @suffix, @name = items, states, prefix, suffix, name
+        @items, @states, @prefix, @suffix, @name, @before, @after = items, states, prefix, suffix, name, [], []
 
         instance_eval(&block) if block
       end