Add assertion after malloc in the message class

Add assertion after malloc in the message class

Since message class is written under presumtion that malloc will never
return NULL(there is no NULL-checking code), it is better to insert an
assertion after malloc was called.

This solves bug reported by SVACE with WGID:
696636 695764 696678 696677 696676 696638 696635 696654 696653 696652
696651 696650 696649 696648 696647 696646 696643 696641 696640 696639

Change-Id: I258a1d141a18283d9b5a5108e82f505ba610c86d
Signed-off-by: SangYoun Kwak <sy.kwak@samsung.com>