Tasklist Block can sometimes crash the Editor

[ianstewart]

See p1703177396699499-slack-C02FMH4G8 and p58i-gah-p2.

Two different reports:

I’m writing a post and I want to convert the bullets to a checklist using the Gutenberg tools. Every time I try to do so from either the p2 front end or the dashboard editor the whole post disappears on me and spits out an error. I converted the bullets to paragraphs by deleting the bullet (not using the transform menu) and then was able to turn the paragraphs into tasks without any trouble.

I was unable to take the first list from this post and turn it into a task list block. Clicking on Task in the Transform To popover would cause the Editor to crash.

[obenland]

It looks like this map call is what's breaking.

[obenland]

Turns out __UNSTABLE_LINE_SEPARATOR was indeed unstable. It was removed in Gutenberg 16.7 WordPress/gutenberg#54310
There is one more instance in p2-blocks that will need to be updated.

[okmttdhr]

This is fixed by https://github.com/Automattic/p2/pull/6237