test: test resolveObject with an empty path

Add a case to test an URL object that has no path at all
for `url.resolveObject`.

PR-URL: #11811
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Yuta Hiroto <[email protected]>
Reviewed-By: Joyee Cheung <[email protected]>