Fix ThemesTest may fail if a third-party theme having theme.js is installed (#40205).

git-svn-id: https://svn.redmine.org/redmine/trunk@22707 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/integration/lib/redmine/themes_test.rb

@@ -23,7 +23,7 @@ class ThemesTest < Redmine::IntegrationTest
 
   def setup
     Redmine::Themes.rescan
-    @theme = Redmine::Themes.themes.last
+    @theme = Redmine::Themes.theme('classic')
     Setting.ui_theme = @theme.id
   end