[Bug] linear-gradient color not work in tooltip icon

[xile611]

Version

2.0.4

Link to Minimal Reproduction

no

Steps to Reproduce

const spec = {
  type: 'bar',
  color: [
    'linear-gradient(to top, #1E90FF, #87CEFA)'
  ],
  legends: {
    visible: true
  },
  data: [
    {
      id: 'barData',
      values: [
        { month: 'Monday', sales: 22 },
        { month: 'Tuesday', sales: 13 },
        { month: 'Wednesday', sales: 25 },
        { month: 'Thursday', sales: 29 },
        { month: 'Friday', sales: 38 }
      ]
    }
  ],
  xField: 'month',
  yField: 'sales'
};

const vchart = new VChart(spec, { dom: CONTAINER_ID });
vchart.renderSync();

// Just for the convenience of console debugging, DO NOT COPY!
window['vchart'] = vchart;

Current Behavior

Expected Behavior

tooltip 中的icon应该显示正确的颜色

Environment

- OS:
- Browser:
- Framework:

Any additional comments?

No response