Add Nullity check for instant service

Add Nullity check for instant service

This code path is now also used by Android. And it may return null. So
add nullity check to avoid crash.

BUG=557285
Committed: https://crrev.com/b4a8cf7a82ae168ea915d44f5997a7e756eca6c6
Cr-Commit-Position: refs/heads/master@{#360433}

[bshe, 2015-11-18 21:38:12]

bshe@chromium.org changed reviewers:
+ sky@chromium.org

[bshe, 2015-11-18 21:38:13]

Hi Scott.
Do you mind to take a look at this simple CL? Thanks!

[sky, 2015-11-18 22:14:27]

LGTM

[bshe, 2015-11-18 22:17:47]

The CQ bit was checked by bshe@chromium.org

[commit-bot: I haz the power, 2015-11-18 22:19:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1456053002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1456053002/1

[commit-bot: I haz the power, 2015-11-18 22:42:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-18 22:43:53]

Patchset 1 (id:??) landed as
https://crrev.com/b4a8cf7a82ae168ea915d44f5997a7e756eca6c6
Cr-Commit-Position: refs/heads/master@{#360433}