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>