emphasis state remain unexpectedly when using gradient

### Version
5.0.2

### Steps to reproduce
```js

option = {
xAxis: {
type: 'category',
data: ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
},
yAxis: {
type: 'value'
},
series: [{
emphasis: {
itemStyle: {
color: 'yellow'
},
focus: 'self'
},
select: {
itemStyle: {
borderWidth: 5
}
},
itemStyle: {
color: {
type: 'linear',
x: 0,
y: 0,
x2: 0,
y2: 1,
colorStops: [{
offset: 0, color: 'red' // 0% 处的颜色
}, {
offset: 1, color: 'blue' // 100% 处的颜色
}],
global: false // 缺省为 false
}
},
selectedMode: true,
data: [150, 230, 224, 218, 135, 147, 260],
type: 'bar'
}]
};
```

+ click a bar and mouseout (the bar will be selected, where it's styled with a border).
+ click the bar again (which brings the state change: 'select' -> 'normal') and rapidly mouseout (before the state animation finished).
+ then the emphasis state (yellow filled) will be remained unexpectedly.


### What is expected?
state transition correct

### What is actually happening?
not correct