When going to new line the size is still displayed as "Heading 1", but changes when start typing

[aliciawood]

When you go to a new line after typing the heading, the font style is still 'heading 1' until you start typing and it changes to 'normal.

Steps for Reproduction

1. Visit https://quilljs.com/playground/
2. Change font style to "heading 1"
3. Type heading, hit enter to go to next line.
4. Observe font style
5. Start typing, observe font style again

Expected behavior:
After hitting enter, the font style should change to 'normal'.

Actual behavior:
After hitting enter, the font style stays as 'heading 1', until the user starts typing.

Version:1.2.4