[JIRA IOT-737] fixed to prevent send coap pdu for no uri

[JIRA IOT-737] fixed to prevent send coap pdu for no uri

if some case is need it to check. the case have to check it.
pdu have to be passed even though there is no uri.

Change-Id: I95ba9b2bb64f7733fcfb3d06b896032c0e3feeef
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3041
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>