Skip adding where clauses when search is empty on DatabaseEngine

[rodrigopedra]

Right now if we search for an empty string, for example in a endpoint that lists all users:

Route::get('/api/users', fn () => User::search(request()->query('q'))->paginate());

Even when the search string is empty, the where clauses are added:

select *
from `users`
where (`users`.`name` like '%%' or `users`.`email` like '%%' or match (`users`.`notes`) against ('' in natural language mode))
order by `id` desc
limit 30 offset 0

Which for the database driver is irrelevant and could lead the query optimizer to pickup a wrong index (when more constraints are added).

If skipping adding the where clauses when the search string is empty is a desirable I can send a PR.

[driesvints]

Yeah I think so. Feel free to PR 👍

[rodrigopedra]

Thanks @driesvints , sent PR #582