Project search error: string contains null byte

Summary

We have strange error, when searching project by one specific query: lab (url looks like https://our-gitlab/search?utf8=%E2%9C%93&snippets=&scope=&search=lab&project_id=222). Any other queries work fine.

I tried to find specific file which causes error with no luck.

What is the current bug behavior?

Searching lab in project returns 500 error. In Sentry we have:

ArgumentError: string contains null byte
  from lib/gitlab/project_search_results.rb:67:in `extname'
  from lib/gitlab/project_search_results.rb:67:in `block (2 levels) in parse_search_result'
  from lib/gitlab/project_search_results.rb:62:in `tap'
  from lib/gitlab/project_search_results.rb:62:in `block in parse_search_result'
  from lib/gitlab/project_search_results.rb:61:in `each_line'
  from lib/gitlab/project_search_results.rb:61:in `each_with_index'
  from lib/gitlab/project_search_results.rb:61:in `parse_search_result'
  from lib/gitlab/file_finder.rb:31:in `block in find_by_content'
  from lib/gitlab/file_finder.rb:31:in `map'
  from lib/gitlab/file_finder.rb:31:in `find_by_content'
  from lib/gitlab/file_finder.rb:17:in `find'
  from lib/gitlab/project_search_results.rb:98:in `blobs'
  from lib/gitlab/project_search_results.rb:18:in `objects'
  from app/services/search_service.rb:46:in `search_objects'
  from app/controllers/search_controller.rb:27:in `show'

Gitlab info

GitLab information
Version:	10.6.0
Revision:	8f82e53
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql

/label ~bug