Fixed authentication issue

Author: Nyholm

lib/Github/HttpClient/Plugin/Authentication.php

@@ -51,7 +51,7 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                     'client_secret' => $this->password,
                 );
 
-                $query .= (false === strpos($query, '?') ? '?' : '&');
+                $query .= empty($query) ? '' : '&';
                 $query .= utf8_encode(http_build_query($parameters, '', '&'));
 
                 $uri = $uri->withQuery($query);
@@ -60,13 +60,14 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
 
             case Client::AUTH_URL_TOKEN:
                 $uri = $request->getUri();
-                $existingQuery = $uri->getQuery();
-                if (!empty($existingQuery)) {
-                    $existingQuery .= '&';
-                }
-                $newQuery = utf8_encode(http_build_query(array('access_token' => $this->tokenOrLogin), '', '&'));
+                $query = $uri->getQuery();
+
+                $parameters = array('access_token' => $this->tokenOrLogin);
 
-                $uri = $uri->withQuery($existingQuery.$newQuery);
+                $query .= empty($query) ? '' : '&';
+                $query .= utf8_encode(http_build_query($parameters, '', '&'));
+
+                $uri = $uri->withQuery($query);
                 $request = $request->withUri($uri);
                 break;