* Fix truncated echo
In typescript, when putting the cursor on a `>` character of an arrow
function, the displayString body comes back as an empty string, and
means the split operation has 0 items, causing a failure when attempting
to call TruncatedEcho.
Even if there's a better fix, I'd assume this is a good safety since we
are injesting external data.
* Convert to use `empty()`
