Haven't tried to narrow it down yet, but maybe related to transactionalizing diffs.
```
Destroying DifferentialDiff PHID-DIFF-kaj3jwg7nzrgimzjhigt...
[2014-11-27 17:55:30] EXCEPTION: (InvalidArgumentException) Argument 1 passed to PhabricatorDestructionEngine::destroyTransactions() must be an instance of PhabricatorApplicationTransaction, null given, called in /core/lib/phabricator/src/applications/system/engine/PhabricatorDestructionEngine.php on line 47 and defined at [<phutil>/src/error/PhutilErrorHandler.php:200]
#0 PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<phabricator>/src/applications/system/engine/PhabricatorDestructionEngine.php:90]
#1 PhabricatorDestructionEngine::destroyTransactions(NULL, string) called at [<phabricator>/src/applications/system/engine/PhabricatorDestructionEngine.php:47]
#2 PhabricatorDestructionEngine::destroyObject(DifferentialDiff) called at [<phabricator>/src/applications/system/management/PhabricatorSystemRemoveDestroyWorkflow.php:98]
#3 PhabricatorSystemRemoveDestroyWorkflow::execute(PhutilArgumentParser) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:394]
#4 PhutilArgumentParser::parseWorkflowsFull(array) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:290]
#5 PhutilArgumentParser::parseWorkflows(array) called at [<phabricator>/scripts/setup/manage_remove.php:21]
```