[BUG]: When IDs are used, it's not possible to update or remove a style

Steps to reproduce

0. https://jsfiddle.net/1cjjr02p/
1. Click the text in editor, change background colour.
2. Export CSS. You'll see both new and original colours exist in an order that prevents the new colour being used.

/* CSS: Output (minus some irrelevant bits) */
#c318{
  background-color:#000000;             /* New colour **/
}
#c318{
  background-color:rgb(152, 77, 77);     /* Original colour **/
}

/* CSS: Expected */
#c318{
  background-color: #000000;     /* New colour **/
}

3.. Using same jsfilddle, it's not possible to remove CSS attribute.

This is similar to #552 #986 but the issue is only present when IDs are used. Classes are cool.