Fix some "expects string, string|false given" issues
Summary:
* /src/applications/config/check/PhabricatorPHPPreflightSetupCheck.php:87 Parameter #1 $string of function strlen expects string, string|false given.
* /src/applications/config/view/PhabricatorSetupIssueView.php:375 Parameter #2 $subject of function preg_match expects string, string|false given.
* /src/applications/config/view/PhabricatorSetupIssueView.php:382 Parameter #2 $subject of function preg_match expects string, string|false given.
* /src/applications/differential/storage/DifferentialHunk.php:229 Parameter #1 $string of function rtrim expects string, string|false given.
* /src/applications/diffusion/engine/DiffusionCommitHookEngine.php:985 Parameter #1 $string of function strlen expects string, string|false given.
* /src/applications/diffusion/engine/DiffusionCommitHookEngine.php:990 Parameter #1 $string of function strlen expects string, string|false given.
* /src/applications/diviner/workflow/DivinerGenerateWorkflow.php:59 Parameter #1 $root of class FileFinder constructor expects string, string|false given.
* /src/applications/drydock/management/DrydockManagementLeaseWorkflow.php:83 Parameter #1 $string of function phutil_json_decode expects string, string|false given.
* /src/applications/harbormaster/management/HarbormasterManagementWriteLogWorkflow.php:78 Parameter #1 $string of function strlen expects string, string|false given.
* /src/applications/harbormaster/management/HarbormasterManagementWriteLogWorkflow.php:79 Parameter #1 $string of function str_split expects string, string|false given.
* /src/applications/repository/storage/PhabricatorRepository.php:2263 Parameter #1 $string of function strlen expects string, string|false given.
* /src/applications/repository/storage/PhabricatorRepository.php:2270 Parameter #1 $string of function strlen expects string, string|false given.
* /src/infrastructure/log/PhabricatorSSHLog.php:38 Parameter #1 $string of function strlen expects string, string|false given.
* /src/infrastructure/log/PhabricatorSSHLog.php:39 Parameter #2 $string of function explode expects string, string|false given.
* /src/infrastructure/ssh/PhabricatorSSHWorkflow.php:104 Parameter #1 $string of function strlen expects string, string|false given.
* /src/infrastructure/ssh/PhabricatorSSHWorkflow.php:112 Parameter #2 $string of function explode expects string, string|false given.
Test Plan: Run static code analysis; read code.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: mainframe98, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26436