suspense fix: Cannot read property 'insertBefore' of undefined

[zakstucke]

Please see #3149 & #3105 for context.

Migrating from React to Preact, our suspense boundaries are failing everywhere with this problem still on latest Preact.

Looking into those specific issues and not finding a solution that worked, I delved into the suspense.js file and played around. The only solution I could find was adding a check for originalParent at the top level of removeOriginal().

I've created a test from the repro in #3149, their way was the only way i could find to simply reproduce.

The change to suspense.js fixes the test.

I'm currently patching preact dist code with this change to make our app work, if this change is wrong and can't be merged, any way of getting round the problem would be greatly appreciated, it's the only thing I've found to work!

[coveralls]

coverage: 99.294%. remained the same when pulling b319cc6 on zakstucke:main into 64be3cb on preactjs:main.

[marvinhagemeister]

Great catch! Thanks for making a PR for this 👍

[zakstucke]

Awesome thanks @marvinhagemeister! Nice to see you managed to understand cause and make the test more clear 🎉