Changed getTokenFromRequest method to handle null value and prevent type error

[eldair]

This code change solves Laravel\Passport\Guards\TokenGuard::getTokenFromRequest(): Return value must be of type string, null returned error which can happen when X-CSRF-TOKEN is missing from the request.

It also aligns getTokenFromRequest method with it's counterpart in VerifyCsrfToken class (which has no return value and handles null value in tokensMatch method)

[hafezdivandari]

I think it is safer to just change the return type to ?string ?

[eldair]

@hafezdivandari hash_equals function which uses the return value of this method requires all arguments to be string

[hafezdivandari]

@eldair yes, that's why we should change the validCsrf method instead, check if the token is not null there.

[eldair]

@hafezdivandari something like this? Partly copied from similar method (tokensMatch) in Illuminate\Foundation\Http\Middleware\VerifyCsrfToken

[hafezdivandari]

Lgtm, thanks.

[taylorotwell]

Tests fail.

[hafezdivandari]

@taylorotwell failed tests are unrelated to changes on this PR and already have been fixed via laravel/framework#55800 (not released yet).

@eldair you may mark this PR as ready again, thanks.