Remove unnecessary empty checks from willFilterPage()

Summary: Fixes T3600. These checks are obsolete after D6512.

Test Plan: Syntax / static / inspection.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3600

Differential Revision: https://secure.phabricator.com/D6563

src/applications/diviner/query/DivinerAtomQuery.php

@@ -75,10 +75,6 @@ final class DivinerAtomQuery
   }
 
   protected function willFilterPage(array $atoms) {
-    if (!$atoms) {
-      return $atoms;
-    }
-
     $books = array_unique(mpull($atoms, 'getBookPHID'));
 
     $books = id(new DivinerBookQuery())