Checked list item loses indentation

[DmitrySkripkin]

When you hit Enter/Return after checked list item, it loses indentation.

Steps for Reproduction

1. Visit codepen.io
2. Set caret after "two"
3. Hit Enter/Return (BTW Shift + Enter/Return works ok)

Expected behavior:
New empty list item with same indent created

Actual behavior:
New empty list item with same indent created, but old list item lose indentation

Ubuntu 16.04, latest Chrome (but I think it doesn't matter):

Version:
1.3.4

[DmitrySkripkin]

checklist enter keyboard handler is the reason, don't know what is the usecase for it. But it works in a different way for checked and unchecked list items.

[jhchen]

The purpose of the handler was to make new checklist items unchecked, but the logic was losing the indent.