Redmine

I'm sorry I need some help.
I have installed a redmine and add some plugins, these are a list of them:

redmine 0.9.0-stable(r3334)
Projects Tree View plugin 0.0.1
Redmine Question plugin Eric Davis 0.3.0
Redmine ezLibrarian plugin 0.1.1
Redmine Vote plugin 0.0.1

When I click a project and come into an overview section, it will appear this error.

and the log info in log/production.log is as following:
Processing WelcomeController#index (for 192.168.8.254 at 2010-01-25 22:55:04) [GET]
Parameters: {"action"=>"index", "controller"=>"welcome"}
Rendering template within layouts/base
Rendering welcome/index
Completed in 128ms (View: 103, DB: 5) | 200 OK [http://192.168.8.254/]

Processing ProjectsController#show (for 192.168.8.254 at 2010-01-25 22:55:06) [GET]
Parameters: {"action"=>"show", "id"=>"redmine", "controller"=>"projects"}
Rendering template within layouts/base
Rendering projects/show

ActionView::TemplateError (undefined method `any?' for nil:NilClass) on line #82 of vendor/plugins/projects_tree_view/app/views/projects/show.rhtml:
79: </div>
80: <% end >
81:
82: < if @members_by_role.any? >
83: <div class="box">
84: <h3 class="icon22 icon22-users"><=l(:label_member_plural)%></h3>
85: <p><% @members_by_role.keys.sort.each do |role| %>

vendor/plugins/projects_tree_view/app/views/projects/show.rhtml:82:in `_run_rhtml_vendor47plugins47projects_tree_view47app47views47projects47show46rhtml'
    app/controllers/projects_controller.rb:164:in `show'
    /usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
    /usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
    /usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
    /usr/lib/ruby/1.8/webrick/server.rb:162:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
    /usr/lib/ruby/1.8/webrick/server.rb:95:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:92:in `each'
    /usr/lib/ruby/1.8/webrick/server.rb:92:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:23:in `start'
    /usr/lib/ruby/1.8/webrick/server.rb:82:in `start'

Rendering /home/redmine/public/500.html (500 Internal Server Error)