Account for multiple multiline spans with empty padding

Account for multiple multiline spans with empty padding

Instead of

```
LL |    fn oom(
   |  __^
   | | _|
   | ||
LL | || ) {
   | ||_-
LL | |  }
   | |__^
```

emit

```
LL | // fn oom(
LL | || ) {
   | ||_-
LL | |  }
   | |__^
   ```