Reactor gives cryptic error on malformed Elm application

[MartinSStewart]

Steps to reproduce:

1. Download program.zip. Alternatively, run elm init and add a src/Main.elm file containing

module Main exposing (..)

a = 5

2. Run elm reactor and open src/Main.elm
3. Note that elm reactor displays a blank page for a while before showing the text

A web handler threw an exception. Details:
thread killed

Expected behavior: Since elm.json states this is an application, this program should result in a compile error.

Note that I've only tested this on Windows with Chrome.

[bryce13950]

I'm getting the same issue on macOS with both Firefox and Safari

[3nt3]

I'm getting the same issue on macOS with Chrome, Firefox and Safari