Undo Issue of blockquote, pre, ordered list and unordered list

[azone]

Expected behavior

All those elements can undo perfectly when double press return(remove those attributes)

Actual behavior

Undo manager reseted in those elements after double press return

Steps to reproduce the behavior

1. input any characters
2. apply them to blockquote, pre, ordered list or unordered list
3. press return
4. press return
5. do undo operation(shake the device)

Tested on iPhone 7, iOS 11, Aztec 1.0.0-beta15