Checking for null ExtensionThrottleEntry.

There are a large number of crashes dereferencing a null
ExtensionThrottleEntry. Temporarily adding a check for null
to eliminate crashes and allow time for further investigation.

TBR=rdevlin.cronin@chromium.org

Bug: 866798
Change-Id: I785c7b907d5377ea42b1452af45d73306b87bd1e
Reviewed-on: https://chromium-review.googlesource.com/1149064
Reviewed-by: Chris Mumford <cmumford@chromium.org>
Commit-Queue: Chris Mumford <cmumford@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577718}
1 file changed