Merge pull request opencv#18517 from alalek:backport_18031

Author: alalek

modules/dnn/src/dnn.cpp

@@ -2113,7 +2113,9 @@ struct Net::Impl : public detail::NetImplBase
 
                     auto ieInpNode = inputNodes[i].dynamicCast<InfEngineNgraphNode>();
                     CV_Assert(oid < ieInpNode->node->get_output_size());
-#if INF_ENGINE_VER_MAJOR_GT(INF_ENGINE_RELEASE_2020_3)
+#if INF_ENGINE_VER_MAJOR_GT(INF_ENGINE_RELEASE_2020_4)
+                    inputNodes[i] = Ptr<BackendNode>(new InfEngineNgraphNode(ieInpNode->node));
+#elif INF_ENGINE_VER_MAJOR_GT(INF_ENGINE_RELEASE_2020_3)
                     inputNodes[i] = Ptr<BackendNode>(new InfEngineNgraphNode(ieInpNode->node->get_output_as_single_output_node(oid)));
 #else
                     inputNodes[i] = Ptr<BackendNode>(new InfEngineNgraphNode(ieInpNode->node->get_output_as_single_output_node(oid, false)));