Check that properties grant_types and scopes exist (#1722)

* Check that the attributes `grant_types` isset rather than property

* Cover `scopes` as well

Author: uintaam

src/Client.php

@@ -164,7 +164,7 @@ public function skipsAuthorization()
      */
     public function hasGrantType($grantType)
     {
-        if (! isset($this->grant_types) || ! is_array($this->grant_types)) {
+        if (! isset($this->attributes['grant_types']) || ! is_array($this->grant_types)) {
             return true;
         }
 
@@ -179,7 +179,7 @@ public function hasGrantType($grantType)
      */
     public function hasScope($scope)
     {
-        if (! isset($this->scopes) || ! is_array($this->scopes)) {
+        if (! isset($this->attributes['scopes']) || ! is_array($this->scopes)) {
             return true;
         }