[IOT-2339] Add NULL check before variable access.

[IOT-2339] Add NULL check before variable access.

Added null check for 'sendData->remoteEndpoint' before the members
of remoteEndpoint gets accessed.

Change-Id: Ic4fc56087bcf9f72233f823ab5aaf0c39ec34afa
Signed-off-by: Senthil Kumar G S <senthil.gs@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/22271
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Harish Marappa <h.marappa@samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>
(cherry picked from commit 1a32ec0a6bf0a691e4abc830d12f5a366aa03321)