Files app: Fix VolumeEntry to not raise error when rootEntry isn't resolved

I faced errors in "isDirectory" during manual tests.

Change-Id: I73fe8b23c3d6dc3bf947fd51083a4cfde8597cda
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1701022
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#677610}
2 files changed