Checking the ewkView value before open clipboard window

Checking the ewkView value before open clipboard window

[Title] Checking the ewkView value before open clipboard window
[Issue#] PLM-P130404-4374
[Problem] Crash occured when open the clipboard window from IME button.
[Cause] Open clipboard window signal callback from IME is registed at EFL, OSP side also, So sometimes ewkView pointer has null value.
[Solution] Checking the ewkView value before open clipboard window. If ewkView value is null then it should be early return before open clipboard window.

Change-Id: Ibff6a2ab3b8c0c0e26fa034cefa54bd59ba69f79