Bug in WebPage Demo

To reproduce:

1. Open https://grapesjs.com/demo.html in incognito mode.

2. Import this code:

<style>* {
  box-sizing: border-box;
  }
  body {
    margin: 0;
  }
  *{
    box-sizing:border-box;
  }
  body{
    margin-top:0px;
    margin-right:0px;
    margin-bottom:0px;
    margin-left:0px;
  }
  h2{
    font-size:50px !important;
  }
  #bck-img7.wrapper-half-left::before{
    background-image:url("/dummy.png") !important;
  }
</style>

3. Clear Canvas

4. Press Import.

Result: The code is not cleared. There is thrash from the previous imported code.

Expected Result: Code should be clean.