Avoid crash in createDevice() if it is called on a Display that did not initialize (e.g. Direct3DCreate9 returned NULL).
Fixed compiler warning.

Landed on behalf of baustin: https://codereview.appspot.com/7794046/.
Review URL: https://codereview.appspot.com/7494048

git-svn-id: http://angleproject.googlecode.com/svn/trunk@2000 736b8ea6-26fd-11df-bfd4-992fa37f6226