[Crash] Touch Events retargeting causes crashes on chrome on android.
https://bugs.webkit.org/show_bug.cgi?id=112210

Reviewed by Dimitri Glazkov.

Added null-check for TouchEvent's touches(), targetTouches() and changedTouches().

No new tests - no new functionality.

* dom/EventRetargeter.cpp:
(WebCore::EventRetargeter::adjustForTouchEvent):
(WebCore::EventRetargeter::adjustTouchList):
* dom/EventRetargeter.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145677 268f45cc-cd09-0410-ab3c-d52691b4dbfc