You don’t need the last ‘$Camera_setting/log =’ just, ‘else empty’ because you want to set the return string value to empty, not the value of $Camera_setting/log to = empty.

  i just want to pass the value of camera ip to camera log 

If your goal is to return the value of $Camera_setting/Camera_IP from a sub microflow or a datasource microflow. Then just set the endpoint return value to $Camera_setting/Camera_IP. If the value is empty it will return empty, otherwise it will return the value. 

If you want to set the value $Camera_setting/log to the value of $Camera_setting/Camera_IP. Then use a change object to change the object $Camera_setting, select member and set it to value $Camera_setting/Camera_IP. Again if the value is empty, then log will be set empty, otherwise the value of $Camera_setting/Camera_IP will be set. No need for an if, the else statement in both cases