fix pass through handling

Author: blink1073

.evergreen/scripts/setup_tests.py

@@ -171,7 +171,7 @@ def handle_test_env() -> None:
 
     # Handle pass through env vars.
     for var in PASS_THROUGH_ENV:
-        if is_set(var) or getattr(opts, var.lower()):
+        if is_set(var) or getattr(opts, var.lower(), ""):
             write_env(var, os.environ.get(var, getattr(opts, var.lower(), "")))
 
     if extra := EXTRAS_MAP.get(test_name, ""):