ignore date range search if search string exclude delimiter

Author: gathuku

lib/ajax-datatables-rails/datatable/column/date_filter.rb

@@ -38,7 +38,7 @@ def range_end
         end
 
         def empty_range_search?
-          (formatted_value == delimiter) || (range_start.blank? && range_end.blank?)
+          formatted_value.exclude?(delimiter) || (formatted_value == delimiter) || (range_start.blank? && range_end.blank?)
         end
 
         # Do a range search