connectivity: Add NULL check across the ca_adapter_net_ssl.c

connectivity: Add NULL check across the ca_adapter_net_ssl.c

[Philippe Coval]

Ported from 1.2-rel to master branch
Conflicts:
	resource/csdk/connectivity/src/adapter_util/ca_adapter_net_ssl.c

Change-Id: If2f43c0150afcb344c290f8bcb21f7647b0daa01
Signed-off-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/16487
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>
Signed-off-by: Philippe Coval <philippe.coval@osg.samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17299
Reviewed-by: Kevin Kane <kkane@microsoft.com>