Blank nodes in list given invalid `.` at start in `text/n3` format.

[jeswr]

Running

import { Parser } from 'n3';
const parser = new Parser({ format: 'text/n3' });
console.log(parser.parse('<s> <p> (_:a).'))

Creates an invalid blank node id of _:.a

This also pops up in https://github.com/eyereasoner/eye-js/pull/1107/files#r1616137075