Structures: Allow null payload in OCEntityHandlerResponse, fix memleak
Structures: Allow null payload in OCEntityHandlerResponse, fix memleak

zqzhang/iotivity-node,zolkis/iotivity-node,zolkis/iotivity-node,zqzhang/iotivity-node,zqzhang/iotivity-node,zolkis/iotivity-node,zqzhang/iotivity-node,zolkis/iotivity-node,zqzhang/iotivity-node,zolkis/iotivity-node