[BUG] Unclosed command literal reports the wrong line

The biggest issue I get with Amber is that one:

```
unsafe $echo

echo 123
echo true
```

That report:

```
Unclosed command literal
at [unknown]:6:1

5| echo true
6|
```

So on long scripts find the line with the issue is a very hard job.
It should says "Unclosed command literal started on line 1".