[Bug] ec-canvas 使用onInit 方法初始化成功之后, setOption 设置notMerge为true报错

### Version

5.3.3

### Link to Minimal Reproduction

https://github.com/ecomfe/echarts-for-weixin/issues/962

### Steps to Reproduce

报错内容

wxml
```
改变图表参数

```

wxss
```
.chart-fa-view {
width: 100%;
height: 566rpx;
}
#mychart-dom-line {
width: 100%;
height: 566rpx;
}
```
js
```
import * as echarts from "../../ec-canvas/echarts";

const app = getApp();
let customChart = null;
function initChart(canvas, width, height, dpr) {
const chart = echarts.init(canvas, null, {
width: width,
height: height,
devicePixelRatio: dpr, // new
});
canvas.setChart(chart);

var option = {
title: {
text: "测试下面legend的红色区域不应被裁剪",
left: "center",
},
legend: {
data: ["A", "B", "C"],
top: 50,
left: "center",
backgroundColor: "red",
z: 100,
},
grid: {
containLabel: true,
},
tooltip: {
show: true,
trigger: "axis",
},
xAxis: {
type: "category",
boundaryGap: false,
axisTick: {
show: false,
},
axisLabel: {
color: "#86909C",
},
// show: false
},
yAxis: {
x: "center",
name: "",
type: "value",
splitLine: {
lineStyle: {
color: "#ccc",
type: "dashed",
},
},
// show: false
},
dataset: {
source: [
["时间", "A", "B"],
["周一", 43.3, 85.8],
["周二", 83.1, 73.4],
["周三", 86.4, 65.2],
["周四", 72.4, 53.9],
],
},
series: [
{
name: "A",
type: "line",
smooth: true,
},
{
name: "B",
type: "line",
smooth: true,
},
],
};
chart.setOption(option);
customChart = chart;
return chart;
}
function getSeries(val) {
if (val % 2 === 0) {
return [
{
name: "A",
type: "line",
smooth: true,
},
{
name: "B",
type: "line",
smooth: true,
},
];
}
return [
{
name: "C",
type: "line",
smooth: true,
},
];
}
function getData(val) {
if (val % 2 === 0) {
return [
["时间", "A", "B"],
["周一", 43.3, 85.8],
["周二", 83.1, 73.4],
["周三", 86.4, 65.2],
["周四", 72.4, 53.9],
];
}
return [
["时间", "C"],
["周一", 90],
["周二", 78],
["周三", 51],
["周四", 12],
];
}

Page({
onShareAppMessage: function (res) {
return {
title: "ECharts 可以在微信小程序中使用啦！",
path: "/pages/index/index",
success: function () {},
fail: function () {},
};
},
data: {
ec: {
onInit: initChart,
},
a: 0,
},

onReady() {},
setChartData() {
this.data.a++;
customChart.setOption(
{
series: getSeries(this.data.a),
dataset: {
source: getData(this.data.a),
},
},
true
);
},
});
```

### Current Behavior

当图表需要更换 series ,setOption 之后,图表会带上没更换之前的 serises 我setOption 设置notMerge 直接报错

### Expected Behavior

设置 notMerge不报错

### Environment

```markdown
- OS:
- Browser:
- Framework:
```

### Any additional comments?

_No response_

Start with the setOption call in setChartData and trace the notMerge path used by the ec-canvas/echarts entry point. Compare the initial series with the replacement series in the reproduction; done means notMerge no longer throws and the old series is removed when the chart is updated.

Written by the indexing model from the issue text.