fix: missing scene issue #255

[NorbertNader]

Overview

This will fix the missing scene issue by safeguard against race condition where the scene gets constructed and immediately removed.

first race condition:

• If componentDidUnload is called before componentDidLoad this.el.isConnected will be false
• This can happen when scrolling page very quickly
• If the component is unmounted before this.setupChartScene is complete we run into a race condition
  where the scene gets created and assigned to this.scene but we override it with null before
  this.setupChartScene calls this.onUpdate
• Without the component mounted there is no point in calling onUpdate since we have nowhere to render this.scene

second race condition:

• if one of the watched props e.g. dataStreams changes this will call onUpdate
• if the component unmounts before this this.scene is set to null
• if we do not have a scene or a component to render it in we should bail

Legal

This project is available under the Apache 2.0 License.