ECharts 6.1.0 compatibility

[joshkel]

Since echarts-gl hasn't yet released an official version with #561 (support for ECharts 6.0.0), I'm experimenting with locally building from master. However, I'm running into problems: On initial render, the chart is blank, and if I click on it, I get errors similar to the following:

ViewGL.js:129 Uncaught TypeError: Cannot read properties of null (reading 'renderer')
    at ViewGL.containPoint (ViewGL.js:129:1)
    at sub._mouseDownHandler (OrbitControl.js:530:1)
    at Eventful.trigger (Eventful.js:103:1)
    at Handler.dispatchToElement (Handler.js:148:1)
    at Handler.<computed> [as mousedown] (Handler.js:248:1)
    at Eventful.trigger (Eventful.js:103:1)
    at HandlerDomProxy.mousedown (HandlerProxy.js:82:1)
    at HTMLDivElement.<anonymous> (HandlerProxy.js:209:1)

This seems to happen with both ECharts 6.0.0 and 6.1.0.