Crash when favicon is requested
https://bugs.webkit.org/show_bug.cgi?id=114624

Patch by peavo@outlook.com <peavo@outlook.com> on 2013-04-15
Reviewed by Brent Fulgham.

* WebIconDatabase.cpp:
(WebIconDatabase::getOrCreateDefaultIconBitmap): Added NULL pointer check.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148456 268f45cc-cd09-0410-ab3c-d52691b4dbfc