symbol disappear when change lines's `series.effect.symbol` property

### Version
4.8.0

### Steps to reproduce
1. set base lines's options with `series.effect.symbol` property:
```js
echarts..setOption({
// ...
series: [{
type: 'lines',
data: [...],
effect: {
show: true,
symbolSize: 10,
symbol: 'triangle'
}
}]
})
```


2. change the symbol type
```js
echarts..setOption({
// ...
series: [{
type: 'lines',
data: [...],
effect: {
show: true,
symbolSize: 10,
symbol: 'circle'
}
}]
})
```


### What is expected?
the lines's symbol changed

### What is actually happening?
symbol disappear