NULL out talk_mediator_ in Shutdown() to avoid crash.
NULL out talk_mediator_ in Shutdown() to avoid crash.

BUG=46283
TEST=manual

Review URL: http://codereview.chromium.org/2755005

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@49584 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