Here's the stack trace, not sure how to repro this yet.
```
[Wed Feb 18 21:18:04.745148 2015] [:error] [pid 21833] [client 172.30.0.99:21300] [2015-02-18 21:18:04] EXCEPTION: (RuntimeException) Undefined variable: transaction at [<phutil>/src/error/PhutilErrorHandler.php:210]
[Wed Feb 18 21:18:04.745282 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #0 PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<phabricator>/src/applications/conpherence/controller/ConpherenceController.php:147]
[Wed Feb 18 21:18:04.745291 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #1 ConpherenceController::renderConpherenceTransactions(ConpherenceThread) called at [<phabricator>/src/applications/conpherence/controller/ConpherenceUpdateController.php:312]
[Wed Feb 18 21:18:04.745296 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #2 ConpherenceUpdateController::loadAndRenderUpdates(string, string, integer) called at [<phabricator>/src/applications/conpherence/controller/ConpherenceUpdateController.php:150]
[Wed Feb 18 21:18:04.745300 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #3 ConpherenceUpdateController::processRequest() called at [<phabricator>/src/aphront/AphrontController.php:33]
[Wed Feb 18 21:18:04.745304 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #4 AphrontController::handleRequest(AphrontRequest) called at [<phabricator>/src/aphront/configuration/AphrontApplicationConfiguration.php:196]
[Wed Feb 18 21:18:04.745308 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #5 AphrontApplicationConfiguration::processRequest(AphrontRequest, PhutilDeferredLog, AphrontPHPHTTPSink) called at [<phabricator>/src/aphront/configuration/AphrontApplicationConfiguration.php:121]
[Wed Feb 18 21:18:04.745312 2015] [:error] [pid 21833] [client 172.30.0.99:21300] #6 AphrontApplicationConfiguration::runHTTPRequest(AphrontPHPHTTPSink) called at [<phabricator>/webroot/index.php:19]
```