web bookmarks crash

Error in command Redcar::WebBookmarks::ShowTree
TypeError: cannot convert instance of class org.jruby.RubySymbol to class [Ljava.lang.Object;
/Users/tim/Devel/projects/redcar/plugins/tree_view_swt/lib/tree_view_swt.rb:32:in `initialize'
/Users/tim/Devel/projects/redcar/plugins/application_swt/lib/application_swt/treebook.rb:24:in `new'
/Users/tim/Devel/projects/redcar/plugins/application_swt/lib/application_swt/treebook.rb:24:in `tree_added'
/Users/tim/Devel/projects/redcar/plugins/application_swt/lib/application_swt/treebook.rb:16:in `to_proc'
/Users/tim/Devel/projects/redcar/plugins/core/lib/core/observable.rb:103:in `call'
/Users/tim/Devel/projects/redcar/plugins/core/lib/core/observable.rb:103:in `observable_run_blocks'
/Users/tim/Devel/projects/redcar/plugins/core/lib/core/observable.rb:103:in `map'
/Users/tim/Devel/projects/redcar/plugins/core/lib/core/observable.rb:103:in `observable_run_blocks'
/Users/tim/Devel/projects/redcar/plugins/core/lib/core/observable.rb:96:in `notify_listeners'
/Users/tim/Devel/projects/redcar/plugins/application/lib/application/treebook.rb:19:in `add_tree'
/Users/tim/Devel/projects/redcar/plugins/web_bookmarks/lib/web_bookmarks/commands.rb:57:in `execute'
/Users/tim/Devel/projects/redcar/plugins/application/lib/application/command/executor.rb:29:in `execute'
/Users/tim/Devel/projects/redcar/plugins/application/lib/application/command.rb:83:in `run'
/Users/tim/Devel/projects/redcar/plugins/application/lib/application/menu/item.rb:45:in `selected'
/Users/tim/Devel/projects/redcar/plugins/application_swt/lib/application_swt/menu.rb:133:in `widgetSelected'
/Users/tim/Devel/projects/redcar/plugins/swt/lib/swt/event_loop.rb:13:in `start'
/Users/tim/Devel/projects/redcar/plugins/core/lib/core/gui.rb:39:in `start'
/Users/tim/Devel/projects/redcar/lib/redcar.rb:180:in `pump'
/Users/tim/Devel/projects/redcar/bin/redcar:30
/Users/tim/Devel/projects/redcar/plugins/application_swt/lib/application_swt/treebook.rb:50:in `create_tree_view': undefined method `model' for nil:NilClass (NoMethodError)
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_folder.rb:79:in `[]'
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_folder.rb:79:in `selection='
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_folder.rb:77:in `each'
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_folder.rb:77:in `selection='
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_item.rb:36:in `activate'
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_label.rb:53:in `activate'
	from /Users/tim/Devel/projects/redcar/plugins/application_swt/lib/swt/vtab_label.rb:76:in `mouseUp'
	from /Users/tim/Devel/projects/redcar/plugins/swt/lib/swt/event_loop.rb:13:in `start'
	from /Users/tim/Devel/projects/redcar/plugins/core/lib/core/gui.rb:39:in `start'
	from /Users/tim/Devel/projects/redcar/lib/redcar.rb:180:in `pump'
	from /Users/tim/Devel/projects/redcar/bin/redcar:30