fix: allow empty userDataDir

[mxschmitt]

#34710 introduced a bug where it used CWD as a userDataDir if none was provided. This fixes it - whats the best way of covering this with a test?

[github-actions]

Test results for "tests 1"

1 fatal errors, not part of any test

8 flaky

⚠️ [chromium-library] › tests/library/headful.spec.ts:233:3 › should click in OOPIF @chromium-ubuntu-22.04-node18
⚠️ [firefox-page] › tests/page/page-evaluate.spec.ts:403:3 › should throw for too deep reference chain @firefox-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/browsercontext-clearcookies.spec.ts:72:3 › should remove cookies by name regex @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/proxy.spec.ts:291:3 › should use SOCKS proxy for websocket requests @webkit-ubuntu-22.04-node18
⚠️ [webkit-library] › tests/library/trace-viewer.spec.ts:1611:1 › canvas clipping @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › tests/page/page-leaks.spec.ts:107:5 › fill should not leak @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › tests/page/page-leaks.spec.ts:161:5 › waitFor should not leak @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › tests/page/page-screenshot.spec.ts:345:5 › page screenshot › should work while navigating @webkit-ubuntu-22.04-node18

38496 passed, 797 skipped
✔️✔️✔️

Merge workflow run.