When using arc patch against a diff on a PHP 8.1 Phorge server, it fails with a strlen(null) error.
Stack Trace:
```
AH01071: Got error 'PHP message: [2023-07-29 10:51:45] EXCEPTION: (RuntimeException) strlen(): Passing null to parameter
#1 ($string) of type string is deprecated at [<arcanist>/src/error/PhutilErrorHandler.php:261]PHP message: arcanist(head=master, ref.master=8130241a11ac, custom=4), phorge(head=master, ref.master=7c1487e4dcfa)PHP message:
#0 <#2> PhutilErrorHandler::handleError(integer, string, string, integer) called at [<phorge>/src/applications/conduit/controller/PhabricatorConduitAPIController.php:293]PHP message:
#1 <#2> PhabricatorConduitAPIController::authenticateUser(ConduitAPIRequest, array, string) called at [<phorge>/src/applications/conduit/controller/PhabricatorConduitAPIController.php:50]PHP message:
#2 phlog(RuntimeException) called at [<phorge>/src/applications/conduit/controller/PhabricatorConduitAPIController.php:111]PHP message:
#3 PhabricatorConduitAPIController::handleRequest(AphrontRequest) called at [<phorge>/src/aphront/configuration/AphrontApplicationConfiguration.php:284]PHP message:
#4 AphrontApplicationConfiguration::processRequest(AphrontRequest, PhutilDeferredLog, AphrontPHPHTTPSink, MultimeterControl) called at [<phorge>/src/aphront/configuration/AphrontApplicationConfiguration.php:204]PHP message:
#5 AphrontApplicationConfiguration::runHTTPRequest(AphrontPHPHTTPSink) called at [<phorge>/webroot/index.php:35]'
```
After fixing this, we then get the following strlen(null) error:
```
AH01071: Got error 'PHP message: [2023-07-29 10:51:45] EXCEPTION: (RuntimeException) strlen(): Passing null to parameter
#1 ($string) of type string is deprecated at [<arcanist>/src/error/PhutilErrorHandler.php:261]PHP message: arcanist(head=master, ref.master=8130241a11ac, custom=4), phorge(head=master, ref.master=7c1487e4dcfa)PHP message:
#0 <#2> PhutilErrorHandler::handleError(integer, string, string, integer) called at [<phorge>/src/applications/differential/conduit/DifferentialGetCommitMessageConduitAPIMethod.php:59]PHP message:
#1 <#2> DifferentialGetCommitMessageConduitAPIMethod::execute(ConduitAPIRequest) called at [<phorge>/src/applications/conduit/method/ConduitAPIMethod.php:156]PHP message:
#2 <#2> ConduitAPIMethod::executeMethod(ConduitAPIRequest) called at [<phorge>/src/applications/conduit/call/ConduitCall.php:131]PHP message:
#3 <#2> ConduitCall::executeMethod() called at [<phorge>/src/applications/conduit/call/ConduitCall.php:81]PHP message:
#4 <#2> ConduitCall::execute() called at [<phorge>/src/applications/conduit/controller/PhabricatorConduitAPIController.php:83]PHP message:
#5 phlog(RuntimeException) called at [<phorge>/src/applications/conduit/controller/PhabricatorConduitAPIController.php:111]PHP message:
#6 PhabricatorConduitAPIController::handleRequest(AphrontRequest) called at [<phorge>/src/aphront/configuration/AphrontApplicationConfiguration.php:284]PHP message:
#7 AphrontApplicationConfiguration::processRequest(AphrontRequest, PhutilDeferredLog, AphrontPHPHTTPSink, MultimeterControl) called at [<phorge>/src/aphront/configuration/AphrontApplicationConfiguration.php:204]PHP message:
#8 AphrontApplicationConfiguration::runHTTPRequest(AphrontPHPHTTPSink) called at [<phorge>/webroot/index.php:35]'
```