diff -r 80c567aff6ee lib/redmine/field_format.rb
--- a/lib/redmine/field_format.rb	Fri Jan 24 10:29:06 2014 +0000
+++ b/lib/redmine/field_format.rb	Thu Jan 30 21:10:09 2014 +0330
@@ -147,7 +147,7 @@
 
       def formatted_value(view, custom_field, value, customized=nil, html=false)
         casted = cast_value(custom_field, value, customized)
-        if custom_field.url_pattern.present?
+        if custom_field.respond_to?(:url_pattern) && custom_field.url_pattern.present?
           texts_and_urls = Array.wrap(casted).map do |single_value|
             text = view.format_object(single_value, false).to_s
             url = url_from_pattern(custom_field, single_value, customized)