fix spellcheck transclusion

[escattone]

Before

After

[peterbe]

Great!
But I actually brought this up because we ought to do a better way to dealing with the error. At the moment, we just log a flaw and fall back the source input. What we perhaps ought to do is something like:

if (macroExecutionErrorHappened()) {
-  html = source
+ html = `<div class="macro-execution-error" title="An error happened here. Bla bla...">${source}</div>` 
}

and then we can put some CSS on that so it stands out a bit more.
It's just a convoluted and fancy way of getting people involved to help you when they see something.

[escattone]

@peterbe Yes, good point. I think we should show something more in these cases.