Fix #3906: safe missing end token error

[helixbass]

Fixes #3906

This fixes the TypeError thrown by the compiler when trying to compile the examples from #3906. All of the examples from that issue except @GeoffreyBooth's should really successfully compile though - I fixed that as well, but figure that the compiler-throwing-an-error part should be merged into master while the fix-wonky-indentation-behavior part should be merged into 2? So I'll open a second pull request against 2 that makes those examples compile successfully

[GeoffreyBooth]

I think at this point, the only fixes that we should be merging into master are fixes for recent regressions. #3906 has been an open issue for over two years, so it shouldn’t be affecting anyone at the moment. I think it can stay unresolved in 1.x and only get fixed in 2. I’m much more concerned that fixing it could create another unintended regression like #4568 (which we should fix in 1.x, if we can find a way to do so without allowing syntax that isn’t possible in 2; @helixbass you’re probably the best one to tackle that if you don’t mind).

@lydell or @jashkenas, do you agree?

[lydell]

Yes, I agree. 👍

[GeoffreyBooth]

@helixbass Can you please retarget this at 2 and/or combine it with #4587?

[helixbass]

@GeoffreyBooth sure, merged this into #4587. And ya I can take a look at #4568