[IOT-2513]NS Fix for static analyzer issues

[IOT-2513]NS Fix for static analyzer issues

1. Removal of Null dereferences.
2. Adding field width specifiers.
3. removing negative checks on unsigned int.

Change-Id: I086c57f3a2473895cd424856f1e9e71af89e10d1
Signed-off-by: abitha.s <abitha.s@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/21515
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
(cherry picked from commit 17afad03deea12a1d61e1bdc758514313109e61e)
Reviewed-on: https://gerrit.iotivity.org/gerrit/21527