Fix variable issue on Conpherence draft saving pathway

Summary:
When we save a Conpherence draft, the draft part works fine but `$xactions` never gets defined, so this gets hit a little later on:

  [24-Feb-2014 11:46:10] WARNING: [pool www] child 82805 said into stderr: "NOTICE: PHP message: [2014-02-24 11:46:10] EXCEPTION: (RuntimeException) Undefined variable: xactions at [/INSECURE/devtools/libphutil/src/error/PhutilErrorHandler.php:211]"
  [24-Feb-2014 11:46:10] WARNING: [pool www] child 82805 said into stderr: "NOTICE: PHP message:   #0 PhutilErrorHandler::handleError(8, Undefined variable: xactions, /INSECURE/devtools/phabricator/src/applications/conpherence/controller/ConpherenceUpdateController.php, 122, Array of size 13 starting with: { request => Object AphrontRequest }) called at [/INSECURE/devtools/phabricator/src/applications/conpherence/controller/ConpherenceUpdateController.php:122]"
  [24-Feb-2014 11:46:10] WARNING: [pool www] child 82805 said into stderr: "NOTICE: PHP message:   #1 ConpherenceUpdateController::processRequest() called at [/INSECURE/devtools/phabricator/webroot/index.php:87]"

Instead, define `$xactions`.

Test Plan:
  - Type into Conpherence while tailing the error log.
  - After patch, clean error log.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D8323