falling into cobweb above a flower pot with a slimeblock below crashes the server

If you jump in multiplayer (it doesn`t happen in singleplayer) on a slimeblock which has a flowerpot ontop with a cobweb above and hit the flowerpot the server crashes. In the serverlist the server is shown online, with the crash-causing Player being online, but it is unjoinable (Read:timeout). I attached the setup and the serverlog.