Fixes bug in MainMenu that if there are no browsers around when timer fires we get a crash.
Fixes bug in MainMenu that if there are no browsers around when timer
fires we get a crash.

BUG=none
TEST=none
TBR=oshima

Review URL: http://codereview.chromium.org/502065

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@34905 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