DAR-1350 Fixed fatal error caused by date collisions in wall_history.

P2: https://wikia-inc.atlassian.net/browse/DAR-1350

This was a fatal error caused by date collisions in the `wall_history` table. It was causing the first sub-query to return more than 1 row. The date collisions were also causing the query to return multiple rows for a single thread. This change fixes both of those issues.