Fix offset-without-limit case in Policy query

Summary: Apparently I am not qualified to do basic math.

Test Plan: Unit test.

Reviewers: vrana

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3218

src/applications/policy/__tests__/PhabricatorPolicyTestCase.php

@@ -133,6 +133,11 @@ final class PhabricatorPolicyTestCase extends PhabricatorTestCase {
       2,
       count($query->setLimit(3)->setOffset(1)->execute()),
       'Offsets work correctly.');
+
+    $this->assertEqual(
+      2,
+      count($query->setLimit(0)->setOffset(1)->execute()),
+      'Offset with no limit works.');
   }
 
 
@@ -165,7 +170,6 @@ final class PhabricatorPolicyTestCase extends PhabricatorTestCase {
   }
 
 
-
   /**
    * Test an object for visibility across multiple user specifications.
    */

src/infrastructure/query/policy/PhabricatorPolicyQuery.php

@@ -153,7 +153,11 @@ abstract class PhabricatorPolicyQuery extends PhabricatorOffsetPagedQuery {
     $limit  = (int)$this->getLimit();
     $count  = 0;
 
-    $need = $offset + $limit;
+    if ($limit) {
+      $need = $offset + $limit;
+    } else {
+      $need = 0;
+    }
 
     $this->willExecute();