visualMap折线区间段颜色混淆

### Version
4.7.0

### Steps to reproduce
```
visualMap:{
show:false,
dimension: 1,
pieces: [

{gte:-10,lte:0,color:'#8bc34a'},
{gt:0,lte:20,color:'#ff5722'},

]
},
```

### What is expected?
在值为大于-10小于等于0的区间，折线应该显示为绿色

### What is actually happening?

实际上在值为0时折线颜色是红色和绿色重叠混合的色值
使用{value: 0，color:'#8bc34a'}指定特定值的颜色也不起效