Didn't check if the transaction was actually created before using it,
which caused a crash.

The revision associated with the cl: 243568
The cl that caused the issue: cl/122453002

BUG=333132

Review URL: https://codereview.chromium.org/133663003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244174 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244174