Linux: fix crash on incognito opening extensions after reordering non-incognito browser action.
Linux: fix crash on incognito opening extensions after reordering non-incognito browser action.

The std::map operator[] inserted default (NULL) pointer on not-found elements which later caused the crash.

BUG=40498
TEST=see bug

Review URL: http://codereview.chromium.org/1517025

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@43980 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,ropik/chromium,ropik/chromium,ropik/chromium,gavinp/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,gavinp/chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium