dlp: handle improper filename in url2path conversion correctly

The file url might contain invalid characters. We cannot create a file
path in that case and thus not grant accessing that file but the
execution of the call can continue as the file path is checked later.

Change-Id: Ie11832b3709e1623f81db5e444d7cb6d7c511aca
Bug: 343630464
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5593977


Reviewed-by: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Commit-Queue: Daniel Brinkers <brinky@google.com>
Cr-Commit-Position: refs/heads/main@{#1311970}