Fix DCHECK failure on bots when registry key can't be opened successfully.
Fix DCHECK failure on bots when registry key can't be opened successfully.

I don't know why this happens, but we should have this sanity check anyway.

BUG=592676
TEST=none
TBR=estade

Review URL: https://codereview.chromium.org/1822263002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#382825}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk