Fix a crash when resolving download display names

display_names could be null, need to do a null check

BUG=937707
TBR=dtrainor@chromium.org

Change-Id: I51e95ee323e81fe1a1e678cb1f6f9cf73f0bc2e4
Reviewed-on: https://chromium-review.googlesource.com/c/1498717
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Min Qin <qinmin@chromium.org>
Auto-Submit: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637200}
1 file changed