Fix a circular reference between Query and Schema

Author: wravery

Introspection.cpp

@@ -67,7 +67,7 @@ std::vector<std::shared_ptr<object::__Type>> Schema::getTypes() const
 
 std::shared_ptr<object::__Type> Schema::getQueryType() const
 {
-	return _query;
+	return _query.lock();
 }
 
 std::shared_ptr<object::__Type> Schema::getMutationType() const

Introspection.h

@@ -41,7 +41,7 @@ class Schema : public object::__Schema
 	std::vector<std::shared_ptr<object::__Directive>> getDirectives() const override;
 
 private:
-	std::shared_ptr<ObjectType> _query;
+	std::weak_ptr<ObjectType> _query;
 	std::shared_ptr<ObjectType> _mutation;
 	std::shared_ptr<ObjectType> _subscription;
 	std::unordered_map<std::string, size_t> _typeMap;