Add a check for null returns from SpellChekerSessonBridge#create().

Add a check for null returns from SpellChekerSessonBridge#create().

When a spell checker service is not available on a device (e.g. Samsung S4)
Android will return a null object and thus SpellCheckerSessionBride will
return null. This CL adds early returns for such cases.

BUG=529355
Committed: https://crrev.com/d6eca98dc5096dc8d739f7d3dd5188c99f1def2a
Cr-Commit-Position: refs/heads/master@{#347849}

[aurimas (slooooooooow), 2015-09-08 23:38:14]

aurimas@chromium.org changed reviewers:
+ rouslan@chromium.org

[aurimas (slooooooooow), 2015-09-08 23:38:14]

PTAL

[please use gerrit instead, 2015-09-09 00:10:00]

lgtm

[aurimas (slooooooooow), 2015-09-09 00:11:02]

The CQ bit was checked by aurimas@chromium.org

[commit-bot: I haz the power, 2015-09-09 00:11:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1310093007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1310093007/1

[commit-bot: I haz the power, 2015-09-09 00:42:41]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-09 00:43:24]

Patchset 1 (id:??) landed as
https://crrev.com/d6eca98dc5096dc8d739f7d3dd5188c99f1def2a
Cr-Commit-Position: refs/heads/master@{#347849}