Broken identical `@keyframes`

[cuongvuong-phoenix]

Description

When defining multiple identical @keyframes, all definitions except the first one are empty.

Reproduction

• Input file:

  @keyframes pulse {
    50% {
      opacity: 0.5;
    }
  }
  
  @keyframes pulse {
    50% {
      opacity: 0.5;
    }
  }

• Output file:

  @keyframes pulse {
    50% {
      opacity: 0.5;
    }
  }
  
  @keyframes pulse {
  }

Environment

• postcss: 8.4.7
• postcss-combine-duplicated-selectors: 10.0.3

[ChristianMurphy]

Pull requests are welcome!