Error 500 on searching word with hyphen

Preconditions:
Create several topics with such words in a title and content: 'he-he', 'no-no', 'so-so'

Steps to reproduce:

1. Go to jcommune and enter search query with 'he-he' or 'no-no' or 'so-so'

Actual result:
Error 500 is shown

Expected result:
Correct display of topics created in precondition