Incorrect underscore handling after --- for em-dash

[codingthat]

An underscore-wrapped phrase immediately after a --- renders plainly instead of in italics.

E.g. it---by design---_cannot have side-effects_. renders like this:

But if you replace the latter --- with —, it works as intended.

So it---by design—_cannot have side-effects_. renders like this:

[gettalong]

Thanks for reporting this bug!

[ashmaroli]

@codingthat This should resolve by inserting spaces around the underscores:

it---by design--- _cannot have side-effects_.

[codingthat]

@ashmaroli Thanks, but not quite: That adds an undesired space between the latter em-dash and the word following it:

As you can see, this is different from the — workaround.

[codingthat]

Thanks @ashmaroli ! =)

[gettalong]

@codingthat I have merged the pull request by @ashmaroli, so I will close this issue.