Fix undefined property in Amazon SES

Summary:
When sending an email through ses, the body property on the response object is not set, throwing a notice. This causes the system to assume a messsage failure, and requeues the email.

As the email is actually delivered, it causes an email bomb :(

Message Undefined property: stdClass::$body
#0 /sidekick/phabricator/phabricator/externals/amazon-ses/ses.php(571): PhutilErrorHandler::handleError(8, 'Undefined prope...', '/sidekick/phabr...', 571, Array)
#1 [internal function]: SimpleEmailServiceRequest->__responseWriteCallback(Resource id #290, '<SendRawEmailRe...')
#2 /sidekick/phabricator/phabricator/externals/amazon-ses/ses.php(526): curl_exec(Resource id #290)
#3 /sidekick/phabricator/phabricator/externals/amazon-ses/ses.php(267): SimpleEmailServiceRequest->getResponse()
#4 /sidekick/phabricator/phabricator/src/applications/metamta/adapter/PhabricatorMailImplementationAmazonSESAdapter.php(33): SimpleEmailService->sendRawEmail('To: brooke.brya...')
#5 /sidekick/phabricator/phabricator/externals/phpmailer/class.phpmailer-lite.php(502): PhabricatorMailImplementationAmazonSESAdapter->executeSend('To: brooke.brya...')
#6 /sidekick/phabricator/phabricator/src/applications/metamta/adapter/PhabricatorMailImplementationPHPMailerLiteAdapter.php(91): PHPMailerLite->Send()
#7 /sidekick/phabricator/phabricator/src/applications/metamta/storage/PhabricatorMetaMTAMail.php(631): PhabricatorMailImplementationPHPMailerLiteAdapter->send()
#8 /sidekick/phabricator/phabricator/src/applications/metamta/management/PhabricatorMailManagementSendTestWorkflow.php(130): PhabricatorMetaMTAMail->sendNow()
#9 /sidekick/phabricator/libphutil/src/parser/argument/PhutilArgumentParser.php(396): PhabricatorMailManagementSendTestWorkflow->execute(Object(PhutilArgumentParser))
#10 /sidekick/phabricator/libphutil/src/parser/argument/PhutilArgumentParser.php(292): PhutilArgumentParser->parseWorkflowsFull(Array)
#11 /sidekick/phabricator/phabricator/scripts/mail/manage_mail.php(28): PhutilArgumentParser->parseWorkflows(Array)
#12 {main}

Test Plan: Send a test email through SES mail provider running on php 5.5

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran, btrahan

Differential Revision: https://secure.phabricator.com/D7660