The code introduced in r21308 for #32116 can trigger an undefined method error in some edge-case(s). See message#67123.
It turns out that it can happen that @Setting.ui_theme.blank?@ returns @false@ while @Redmine::Themes.theme(Setting.ui_theme)@ returns @nil@. This is not expected while sending a message to @Redmine::Themes.theme(Setting.ui_theme).javascripts.include?@ in source:/trunk/lib/redmine/info.rb@21529#L25.

The error can be reproduced (manually) on the console by setting a non-existing value for @Setting.ui_theme@ like e.g. @Setting.ui_theme = 'foo'@ and subsequently sending a message to @Redmine::Info.environment@. This effectively simulates the edge-case that is reported in the forum thread by "Greg G":/users/584287.

This can be solved by changing lines 23-32 in source:/trunk/lib/redmine/info.rb@21529#L23 from:

        theme = Setting.ui_theme.blank? ? 'Default' : Setting.ui_theme.capitalize
        unless Setting.ui_theme.blank?
          theme_js  = (if Redmine::Themes.theme(Setting.ui_theme).javascripts.include?('theme')
                         ' (includes JavaScript)'
                       else
                         ''
                       end
                      )
        end
        theme_string = (theme + theme_js.to_s).to_s

        theme_string = ''
        theme_string += (Setting.ui_theme.blank? ? 'Default' : Setting.ui_theme.capitalize)
        unless Setting.ui_theme.blank? ||
               Redmine::Themes.theme(Setting.ui_theme).nil? ||
               !Redmine::Themes.theme(Setting.ui_theme).javascripts.include?('theme')
          theme_string += ' (includes JavaScript)'
        end

This change also fixes the issue that the @theme_js@ variable is defined conditionally but is unconditionally "used", which I feel is bad practice.

This issue affects 5.0.0 and current source:/trunk@21529.