canvas2d，真机调试时报错？(U.createEvent is not a function)

报错完整信息:

MiniProgramError U.createEvent is not a function TypeError: U.createEvent is not a function

经过测试，使用如下代码的exec时会报错，去掉exec后就不报错了。

// js
 wx.createSelectorQuery()
      .select('#canvas')
      .fields({
        node: true,
        size: true,
      })
      .exec(this.init.bind(this))
// wxml
<canvas
  type="2d"
  id="canvas"
  style="width: 300px; height: 300px;"
></canvas>