error when closure param lists aren't terminated by | (#14095)

Fixes #13757, fixes #9562

# User-Facing Changes

- `unclosed |` is returned for malformed closure parameters:

```
{ |a }
```

- Parameter list closing pipes are highlighted as part of the closure

crates/nu-parser/src/parser.rs

@@ -4594,7 +4594,7 @@ pub fn parse_closure_expression(
                 } = token.1
                 {
                     end_span = Some(span);
-                    amt_to_skip = token.0;
+                    amt_to_skip += token.0;
                     break;
                 }
             }
@@ -4602,6 +4602,7 @@ pub fn parse_closure_expression(
             let end_point = if let Some(span) = end_span {
                 span.end
             } else {
+                working_set.error(ParseError::Unclosed("|".into(), Span::new(end, end)));
                 end
             };