This is to fix arc unit when running a test file with no test results (e.g. skipped)
EXCEPTION: (RuntimeException) Undefined variable: last_test_finished at [<phutil>/src/error/PhutilErrorHandler.php:210] arcanist(head=master, ref.master=d54cb072facd), deviantart(), phutil(head=master, ref.master=75f675747648) #0 PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<arcanist>/src/unit/parser/ArcanistPhpunitTestResultParser.php:95] #1 ArcanistPhpunitTestResultParser::parseTestResults(string, string) called at [<deviantart>/unit/DaUnitEngine.php:150] #2 DaUnitEngine::parseTestResults(string, TempFile, string, string) called at [<deviantart>/unit/DaUnitEngine.php:82] #3 DaUnitEngine::run() called at [<arcanist>/src/workflow/ArcanistUnitWorkflow.php:186] #4 ArcanistUnitWorkflow::run() called at [<arcanist>/scripts/arcanist.php:382]