Fix No SD issue for PDU Session Establishment Accept

src/nas/ies/SNSSAI.c

@@ -45,7 +45,8 @@ int encode_snssai(SNSSAI snssai, uint8_t iei, uint8_t* buffer, uint32_t len) {
 
   ielen = snssai.len;
 
-  if (snssai.sd == 0) ielen = 1;  // Don't include SD if it = 0
+  if (snssai.sd == 0xffffff)
+    ielen = SST_LENGTH;  // TODO: Don't include SD if it = 0xffffff
 
   *(buffer + encoded) = ielen;
   encoded++;

src/smf_app/smf_n1.cpp

@@ -201,7 +201,11 @@ bool smf_n1::create_n1_pdu_session_establishment_accept(
   // sm_msg->pdu_session_establishment_accept.gprstimer.timeValue = 0;
 
   // SNSSAI
-  sm_msg->pdu_session_establishment_accept.snssai.len = SST_AND_SD_LENGTH;
+  if (sm_context_res.get_snssai().sd == SD_NO_VALUE) {
+    sm_msg->pdu_session_establishment_accept.snssai.len = SST_LENGTH;
+  } else {
+    sm_msg->pdu_session_establishment_accept.snssai.len = SST_AND_SD_LENGTH;
+  }
   sm_msg->pdu_session_establishment_accept.snssai.sst =
       sm_context_res.get_snssai().sst;
   sm_msg->pdu_session_establishment_accept.snssai.sd =