[ticket/13188] Add missing where clause to post_id query in sphinx index

PHPBB3-13188
[ticket/13188] Correctly format string concatenation

PHPBB3-13188
Merge pull request #3048 from naderman/ticket/13188

[ticket/13188] Add missing where clause to post_id query in sphinx index
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/13188] Correctly format string concatenation
  [ticket/13188] Add missing where clause to post_id query in sphinx index