After sampling not all series with same x-axis will display on single tooltip.

### Version
5.1.2

### Steps to reproduce
```
myChart.setOption({
series:[
{
sampling: 'lttb',
type: 'line',
data: Array.from(new Array(2000)).map((x, i) => [i, Math.floor(Math.random() * (5 - 1 1)) 1]),
},
{
sampling: 'lttb',
type: 'line',
data: Array.from(new Array(2000)).map((x, i) => [i, Math.floor(Math.random() * (10 - 1 1)) 1]),
}
],
xAxis:[{type:'value'}],
yAxis:[{type:'value', max: 15, min: 0}],
tooltip: {
trigger: 'axis',
},
dataZoom: [
{
xAxisIndex: [0, 1],
type: 'inside',
filterMode: 'filter'
}
]
})
```

### What is expected?
Display all values with same x-axis after sampling.

### What is actually happening?
Some values is not displayed.