The fixer node may get removed when merging adjacent inlines, so move
the cleanup to before this. For safety, also properly check for non-null
nodes so we don't crash if it's still elided for some reason.
There seems to be a bug in Chrome where it will sometimes not render
some of the text in the DOM when there are multiple zero-width spaces
around the beginning and ends of inline tags (not sure on the exact
details).
Steps to reproduce (prior to this commit):
1. Turn on bold and underlined text
2. Type something in bold and underlined text
3. Turn off bold and underline
4. Try to type something — it will not show up! That is, until you press
the enter key and we remove the zero-width spaces.
This is a massive refactor to port Squire to TypeScript, fix a bunch of small
bugs and modernise our tooling. The development was done on an internal
repository, so apologies to anyone following externally for the commit dump;
updates from here should come as real commits again.
Co-authored-by: Joe Woods <woods@fastmailteam.com>
