Replace empty() by more strict checks (#1125)

* Replace empty() by stricter checks

* Apply StyleCI fixes

* Compare with empty string instead of checking length

* Compare with empty array instead of checking count

* Compare with empty string instead of checking length

Author: jbelien

Provider/AbstractHttpProvider.php

@@ -96,7 +96,7 @@ protected function getParsedResponse(RequestInterface $request): string
         }
 
         $body = (string) $response->getBody();
-        if (empty($body)) {
+        if ('' === $body) {
             throw InvalidServerResponse::emptyResponse((string) $request->getUri());
         }