docs(queries): Fix throwing exception problem (#850)

* docs(queries): Fix throwing exception problem

* fix routes

* use Graphql Erorr

doc/queries/nodes.md

@@ -39,6 +39,9 @@ Now we have an "Article" type in the schema with three fields `id`, `label` and
 To add the resolvers we go to our schema implementation and call the appropriate data producers inside the `getResolverRegistry` method. Because our types are extending a common `NodeInterface` we need to also tell what to resolve for a particular type, otherwise it could be an Article or a Page.
 
 ```php
+use GraphQL\Error\Error;
+...
+
 /**
  * {@inheritdoc}
  */

doc/queries/routes.md

@@ -36,6 +36,9 @@ In this schema we can see that we can query a node by its route, that takes a pa
 To add the resolvers we go to our schema implementation and call the appropriate data producers inside the `getResolverRegistry` method.
 
 ```php
+use GraphQL\Error\Error;
+...
+
 /**
  * {@inheritdoc}
  */