Fix one encoding error

Author: mashedcode

plugin/notmuch.rb

@@ -201,7 +201,7 @@ def search_render(search)
       authors = e.authors.to_utf8.split(/[,|]/).map { |a| author_filter(a) }.join(',')
       date = Time.at(e.newest_date).strftime(date_fmt)
       subject = e.messages.first['subject']
-      subject = Mail::Field.new('subject', subject).to_s
+      subject = Mail::Field.new('subject', subject).to_s.to_utf8
       buffer << '%-12s %3s %-20.20s | %s (%s)' % [date, e.matched_messages, authors, subject, e.tags]
       $curbuf.threads << e.thread_id
     end