Rollup merge of #87646 - JohnTitor:fix-parser-ice, r=oli-obk

Fix a parser ICE on invalid `fn` body

Fixes #87635
A better fix would add a check for `fn` body on `expected_one_of_not_found` but I haven't come up with a graceful way. Any idea?
r? ```@oli-obk``` ```@estebank```

compiler/rustc_parse/src/parser/item.rs

@@ -1714,13 +1714,11 @@ impl<'a> Parser<'a> {
                     // the AST for typechecking.
                     err.span_label(ident.span, "while parsing this `fn`");
                     err.emit();
-                    (Vec::new(), None)
                 } else {
                     return Err(err);
                 }
-            } else {
-                unreachable!()
             }
+            (Vec::new(), None)
         };
         attrs.extend(inner_attrs);
         Ok(body)