lwfs error NG

(swf2lwf -i -f gui_med_fla.fla gui_med_fla.swf atlas.json)
swf2lwf caused an exception:
undefined method `graphic_objects' for nil:NilClass
backtrace:
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lib/swf2lwf/swf2lwf.rb:1945:in `parse_define_button2'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lib/swf2lwf/swf2lwf.rb:2631:in `parse_tags'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lib/swf2lwf/swf2lwf.rb:2680:in `parse_swf'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lib/swf2lwf/swf2lwf.rb:3444:in `swf2lwf'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lib/swf2res.rb:71:in `swf2res'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lwfs.rb:638:in `block in convert'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lwfs.rb:617:in `each'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lwfs.rb:617:in `convert'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lwfs.rb:390:in `block (3 levels) in '
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lwfs.rb:373:in `catch'
C:/cocos2d/lwfs/build/win/LWFS/.a/lwfs/lwfs.rb:373:in `block (2 levels) in '