in IE, incorrect enter key behavior with block element in a list item

[alissa]

steps for recreation:

1. type in some text
2. select all format as some header
3. select all and format as list
4. place the cursor at the middle of the first list item
5. press enter twice

(you already have a weird gap between lines 2 and 3)

6. press up arrow twice
7. write something
8. go 1 down and write something

-> you got

<ol>
	<li>
	<h1>as</h1>
	</li>
	<li>sdf
	<h1>sdf</h1>
	</li>
	<li>
	<h1>df</h1>
	</li>
</ol>

there is some text that is inside the li but outside the h1.

(i saw a similar ticket but for ck3 #4927)