Merge branch 'fix_encode_nas_header' into 'develop'

Fix encoding NAS header

See merge request oai/cn5g/oai-cn5g-smf!193

src/nas/nas_message.c

@@ -366,6 +366,7 @@ static int _nas_message_header_encode(
       ENCODE_U8(buffer + size, header->sequence_number, size);
     }
   }
+  return size;
 }
 
 static int _nas_message_protected_encode(