gtk views: NULL-check fixed_ before hiding
gtk views: NULL-check fixed_ before hiding

Due to a bug in the test setup, these critical errors were not causing
DCHECKs.  Fixing that bug caused this bug to become more visible.

BUG=62868
TEST=no more critical errors in ExtensionApiTest.GetViews and others

Review URL: http://codereview.chromium.org/4856001

git-svn-id: http://src.chromium.org/svn/trunk/src@65891 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 2c94222b2ee1cc0f703e5076e743da8c21b7913c
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser