cannot uncomment lines inside function bodies

uncommenting lines in the text editor (``) doesn't work if the cursor (or selection) is inside a function body:

```
CREATE "my_func"() RETURNS VOID AS $$
-- RAISE NOTICE 'try uncommenting me';
RETURN;
$$;
```

Start with the text editor's Cmd+/ comment-toggle handling, using the SQL function-body example in the issue as the reproduction case. Trace why a cursor or selection inside the body is skipped, then verify that the commented RAISE NOTICE line can be toggled and that behavior outside function bodies still works.

Written by the indexing model from the issue text.