Fix `new` and `old` fields in code locations — radicle-explorer

Instead of being nullable() the new and old fields in a code location are optional.

 export const codeLocationSchema = object({
   commit: string(),
   path: string(),
   old: rangeSchema.nullable(),
   new: rangeSchema.nullable(),
   old: rangeSchema.optional(),
   new: rangeSchema.optional(),
 });
 export type Author = z.infer<typeof authorSchema>;