Line Streaming Visualization .. session freez if size parameter is not included

[Siouffy]

Ive tried the line streaming visualization using the UI at the server and the python api ... in both cases, if we dont specify the size parameter (which is supposedly optional) the session will stall, causing even old visualizations to disappear... A quick fix would be to init the size param to deafult values or just make it as required parameter instead of optional ...