I'm seeing a bunch of these in our error logs:
```
[12-Oct-2014 10:21:33 UTC] [2014-10-12 21:21:33] ERROR 2: Invalid argument supplied for foreach() at [/usr/src/phabricator/src/applications/differential/customfield/DifferentialReviewersField.php:186]
[12-Oct-2014 10:21:33 UTC] #0 DifferentialReviewersField::validateCommitMessageValue(NULL) called at [<phabricator>/src/applications/differential/conduit/DifferentialParseCommitMessageConduitAPIMethod.php:74]
[12-Oct-2014 10:21:33 UTC] #1 DifferentialParseCommitMessageConduitAPIMethod::execute(ConduitAPIRequest) called at [<phabricator>/src/applications/conduit/method/ConduitAPIMethod.php:65]
[12-Oct-2014 10:21:33 UTC] #2 ConduitAPIMethod::executeMethod(ConduitAPIRequest) called at [<phabricator>/src/applications/conduit/call/ConduitCall.php:163]
[12-Oct-2014 10:21:33 UTC] #3 ConduitCall::executeMethod() called at [<phabricator>/src/applications/conduit/call/ConduitCall.php:90]
[12-Oct-2014 10:21:33 UTC] #4 ConduitCall::execute() called at [<phabricator>/src/applications/conduit/controller/PhabricatorConduitAPIController.php:88]
[12-Oct-2014 10:21:33 UTC] #5 PhabricatorConduitAPIController::processRequest() called at [<phabricator>/webroot/index.php:101]
```