[Bug] 热力图Y轴渲染错误

### Version

5.6.0

### Link to Minimal Reproduction

No response

### Steps to Reproduce

```js
export const getHeatOptions = (): E.EChartsOption => {
return {
tooltip: {
position: 'top',
},
grid: {
top: "1%",
bottom: "10%",
left: "1%",
right: "1%",
containLabel: true
},
xAxis: {
type: 'category',
data: hours as any,
axisTick: {
lineStyle: {
color: '#fff'
}
},
axisLabel: {
color: '#fff',
},
splitArea: {
show: true,
areaStyle: {
color: ['rgba(44,60,77,.8)', 'rgba(35,47,68,.7)']
}
}
},
yAxis: {
type: 'category',
data: [],
axisTick: {
show: true,
lineStyle: {
color: '#fff'
}
},
axisLabel: {
color: '#fff'
},
splitArea: {
show: true,
areaStyle: {
color: ['rgba(44,60,77,.8)', 'rgba(35,47,68,.7)']
}
}
},
visualMap: {
min: 0,
max: 3600,
calculable: true,
orient: 'horizontal',
left: 'center',
textStyle: {
color: '#fff'
},
inRange: {
color: ['#313695', '#4575b4', '#74add1', '#abd9e9', '#e0f3f8', '#ffffbf', '#fee090', '#fdae61', '#f46d43', '#d73027', '#a50026']
}
},
series: {
type: 'heatmap',
data: [],
label: {
show: true
},
emphasis: {
itemStyle: {
shadowBlur: 10,
shadowColor: 'rgba(0, 0, 0, 0.5)'
}
}
}
}
}
````
### Current Behavior

### 左上角渲染错误
### **排除发现去的Y轴配置项splitArea的显示也可以正常显示，或者数据项在某些情况下也正常。如图：**

### Expected Behavior

正常渲染

### Environment

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

### Any additional comments?

_No response_