R1:00a20d3cdc54

Fix various "strlen(null)" PHP 8.1 issues on "bin/phd" and "bin/drydock" pathways

Summary: Ref T13676. Ref T13588. Fix some issues that prevent "bin/phd" and "bin/drydock" from executing under PHP 8.1, broadly because `null` is being passed to `strlen()`.

Test Plan: Ran `bin/phd debug task` and `bin/drydock ...` under PHP 8.1.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13676, T13588

Differential Revision: https://secure.phabricator.com/D21795