[EFL] MiniBrowser's window_create may return NULL
https://bugs.webkit.org/show_bug.cgi?id=139585

Reviewed by Gyuyoung Kim.

Move NULL checking before using object which window_create
returns.

* MiniBrowser/efl/main.c:
(elm_main):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@177256 268f45cc-cd09-0410-ab3c-d52691b4dbfc