500 error when viewing the first commit

Created by: saschagrunert

Hi there, I am at version 3.1. If I want to view the first commit I get an 500 error:

  Rendered notes/_per_line_note_link.html.haml (0.1ms)
  Rendered notes/_per_line_note_link.html.haml (0.1ms)
  Rendered notes/_per_line_note_link.html.haml (0.1ms)
  Rendered notes/_per_line_note_link.html.haml (0.1ms)
  Rendered commits/_text_file.html.haml (56.5ms)
  Rendered commits/_diffs.html.haml (184.8ms)
  Rendered commit/show.html.haml within layouts/project_resource (267.6ms)
Completed 500 Internal Server Error in 364ms

ActionView::Template::Error (undefined method `tree' for nil:NilClass):
    43:         - if file.text?
    44:           = render "commits/text_file", diff: diff, index: i
    45:         - elsif file.image?
    46:           - old_file = (@commit.prev_commit.tree / diff.old_path)
    47:           - if diff.renamed_file || diff.new_file || diff.deleted_file
    48:             .diff_file_content_image
    49:               .image{class: image_diff_class(diff)}
  app/views/commits/_diffs.html.haml:46:in `block in _app_views_commits__diffs_html_haml___2227032179520999248_17281546820'
  app/views/commits/_diffs.html.haml:16:in `each'
  app/views/commits/_diffs.html.haml:16:in `each_with_index'
  app/views/commits/_diffs.html.haml:16:in `_app_views_commits__diffs_html_haml___2227032179520999248_17281546820'
  app/views/commit/show.html.haml:2:in `_app_views_commit_show_html_haml__976444024044534118_17282999060'


Started GET "/static.css" for 217.235.73.238 at 2012-12-01 18:53:41 +0100
Processing by ProjectsController#show as HTML
  Parameters: {"id"=>"static.css"}
  Rendered public/404.html (0.4ms)
Filter chain halted as :project rendered or redirected
Completed 404 Not Found in 14ms (Views: 10.9ms | ActiveRecord: 0.7ms)

What could be the problem? Thanks 👍