Memory leak when enable `grid3D.postEffect`

[troy351]

• dispose and create echarts instance with the same option on the same dom node many times
• with grid3D.postEffect.enabled: true
• without grid3D.postEffect.enabled: true

[troy351]

Possible reproduce code

let myChart;

setInterval(() => {
  if (myChart) myChart.dispose();

  myChart = echarts.init(dom, null, {
    renderer: "canvas",
  });

  myChart.setOption(option);
}, 100);

• without postEffect: everything works
• with postEffect shows error after a few seconds, which also proves memory leak

[troy351]

@pissang