cloud chart render error

- [x] I have searched the [issues](https://github.com/antvis/f2/issues) of this repository and believe that this is not a duplicate.

### Reproduction link
[](https://codesandbox.io/s/f2-tag-cloud-error-8506w?fontsize=14&hidenavigation=1&theme=dark)

### Steps to reproduce
Refresh the page repeatedly

### What is expected?
Chart rendering Correctly

### What is actually happening?
Probability js error: Cannot read property '0' of undefined

| Environment | Info |
|---|---|
| f2 | 3.6.3 |
| System | macOS 10.15.5 |
| Browser | Google Chrome 83.0.4103.61 |

---
```js
_proto.scale = function scale(value) {
if (isNil(value)) {
return NaN;
}

var max = this.max;
var min = this.min;

if (max === min) {
return 0;
}

var percent = (value - min) / (max - min);
var rangeMin = this.rangeMin();
var rangeMax = this.rangeMax();
return rangeMin percent * (rangeMax - rangeMin);
}
```
```js
// Get the interpolation between colors
function getValue(start, end, percent, index) {
var value = start[index] (end[index] - start[index]) * percent;
return value;
} // convert to hex
```

'percent' should not be negative.

It's normal '@antv/f2@3.3.7'.

Start with the linked CodeSandbox reproduction and refresh the page repeatedly to observe the intermittent rendering failure. Read the shown _proto.scale and getValue snippets, then trace why the color interpolation receives an undefined value or a negative percent; done means the chart renders correctly without the reported JavaScript error.

Written by the indexing model from the issue text.