[8.x] Makes the retrieval of Http client transferStats safe

[lukeraymonddowning]

Hello there!

The Http Client returns some really nice details in the handlerStats method. However, when faking a request inside a test, the transferStats object is null. This causes an error when attempting to call the handlerStats method. This PR updates the handlerStats call by wrapping it in an optional call and returning an empty array by default. This makes consuming code much cleaner by no longer requiring a try/catch statement.

Http::fake(['example.com' => Http::response()]);

// Before
try {
    $stats = Http::get('example.com')->handlerStats();
} catch ($e) {
    $stats = [];
}

// After
$stats = Http::get('example.com')->handlerStats()['some_stat'] ?? null;

There is another option, which is that we return a new Fluent from handlerStats, but that would be a breaking change because previous try/catches would now pass but return null, which could cause undesired side-effects. If that is desirable to you, let me know and I'll write a PR for 9.x that will expand on this one.

Thanks for your time guys :-)

Regards,
Luke

[lukeraymonddowning]

I've also added in support for effectiveUri, which was also throwing an error when faking requests. It will now return null when faked.