Single (inline) pipe is mistakenly (?) interpreted as multiline indicator

When rendering a single pipe on the same line as the tag, Haml swallows the pipe — presumably because it’s interpreted as multiline indicator (http://haml.info/docs/yardoc/file.REFERENCE.html#multiline):

```haml
%span |
```
is evaluated to:
```html
<span></span>
```
In my eyes (and I understand that this might very well be just a matter of opinion) that’s incorrect or at least unexpected behavior, as this case contains only a single pipe, not *multiple*. IMO the pipe should be treated as a regular string in this case.

The attached test illustrates the issue.