Crash when searching with before/after

Running Ruby 1.9.1 with all updated gems. Crash occurs whenever searching something like "after:2013" or "before:8/20". Really any use of before/after seems to trigger a crash. Contents of ~/.sup/exception-log.txt:

```
--- Redwood::Util::Query::QueryDescriptionError from thread: main
Xapian::Query(VALUE_RANGE 2 �]!��� �d)
/home/pinaki/.gem/ruby/1.9.1/gems/sup-0.14.0/lib/sup/util/query.rb:9:in `describe'
/home/pinaki/.gem/ruby/1.9.1/gems/sup-0.14.0/lib/sup/index.rb:495:in `parse_query'
/home/pinaki/.gem/ruby/1.9.1/gems/sup-0.14.0/lib/sup/util.rb:639:in `method_missing'
/home/pinaki/.gem/ruby/1.9.1/gems/sup-0.14.0/lib/sup/modes/search_results_mode.rb:43:in `spawn_from_query'
/home/pinaki/.gem/ruby/1.9.1/gems/sup-0.14.0/bin/sup:303:in `<module:Redwood>'
/home/pinaki/.gem/ruby/1.9.1/gems/sup-0.14.0/bin/sup:73:in `<top (required)>'
/home/pinaki/.gem/ruby/1.9.1/bin/sup:23:in `load'
/home/pinaki/.gem/ruby/1.9.1/bin/sup:23:in `<main>'
```