Fix model type checking causing some crashes.
Fix model type checking causing some crashes.

BUG=62991
TEST=unit and sync integration

Review URL: http://codereview.chromium.org/4905001

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@65991 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser