JS example runs once, throws 500s afterward

[squillace]

Clean install from 63696dd.

just build works fine

just run-js runs ONCE. after that it returns 500:

squillace@idiopath: curl http://localhost:3000
Hello, JS wasi:http world!
squillace@idiopath: curl http://localhost:3000
Error reading body

A case for using the debugger!!!