Fix crash in debug mode

:Release Notes:
Check jvalue type before usage.

:Detailed Notes:

:Testing Performed:
Automatic tests in debug mode succeeded.

:QA Notes:

:Issues Addressed:
[GF-3287] Support removing properties on pbnjson objects

Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>

Change-Id: I255fa9fffb22664960bed2d7de4e7b9c9a22eab2
Reviewed-on: https://g2g.palm.com/3231
Reviewed-by: Build Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>
Tested-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>