Minor code cleanup by removing duplicated null checks
https://bugs.webkit.org/show_bug.cgi?id=113701

Reviewed by Darin Adler.

Duplicated null check is code redundancy, so delete those.

* editing/FrameSelection.cpp:
(WebCore::FrameSelection::setFocusedNodeIfNeeded):
* platform/Arena.cpp:
(WebCore::FreeArenaList):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147333 268f45cc-cd09-0410-ab3c-d52691b4dbfc