[EFL] [WK2] Don't call eina_iterator_free() if iterator is NULL

[EFL] [WK2] Don't call eina_iterator_free() if iterator is NULL
https://bugs.webkit.org/show_bug.cgi?id=90076

Patch by Sudarsana Nagineni <sudarsana.nagineni@linux.intel.com> on 2012-07-03
Reviewed by Kenneth Rohde Christiansen.

Add a null check to prevent calling eina_iterator_free() when
iterator is NULL.

No new tests. This patch doesn't change behavior.

* platform/efl/FileSystemEfl.cpp:
(WebCore::listDirectory): Early return when iterator is NULL.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121752 268f45cc-cd09-0410-ab3c-d52691b4dbfc