Workaround to prevent a crash checking extensions blacklist.
Workaround to prevent a crash checking extensions blacklist.

Somehow the extensions dictionary is ending up null when we don't expect it to.
This prevents the crash but may not prevent other problems. 

BUG=29317
TEST=none


Review URL: http://codereview.chromium.org/507030

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@34808 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