Fix crash when reloading config.rb

[benedikt]

The previous implementation cached the reactor on the extension instance. However, the instance doesn’t survive the reload and would try to create a new reactor. This failed, because the previous reactor wasn’t stopped.

This change caches the reactor in the ractor class itself so it’s still there after the reload.

[sandstrom]

Thanks @benedikt!

I'm no longer using this code, so I cannot verify that your code actually works 😬

How much have you tested this code? I'm willing to merge anyway, because it seems like a low-risk PR. But good to know how much testing you've done on your end.

[benedikt]

@sandstrom Thanks! It works on my machine 😂

[sandstrom]

thanks @benedikt