Fix static analysis issue in ocresource

Fix static analysis issue in ocresource

- add initial value and null checking

Change-Id: I50731d23865c72d2c03cb3b149b19bf4236bf587
Signed-off-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/14955
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Ziran Sun <ziran.sun@samsung.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>
(cherry picked from commit 2bf1598fa14d918f3c254feaedd61716cba8d0f1)
Reviewed-on: https://gerrit.iotivity.org/gerrit/15101
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>