Howdy doody, this little line is throwing and reported via one of my repos.

Minimal Repro:

import * as z from 'zod';

console.log(
  z.toJSONSchema(
    z
      .string()
      .meta({ id: 'foo', description: 'foo' })
      .describe('bar')
      .optional(),
  ),
);

To be honest, I haven't taken too much time to understand what this bit of code is doing but adding a conditional before seems to work.

Resolves samchungy/fastify-zod-openapi#352