fix: void calls with no args now generate call/return nodes.

         * @param iterator An iterator over a GraphNode's variable actions, which will be consumed

         *                 until the closing CallMarker that matches callMarker is found.

         * @param callMarker The call marker that enters the call to be analyzed.

         * @return The list of nodes, inserted into the graph and connected to each other.

         * @return The non-empty list of nodes, inserted into the graph and connected to each other.

         *     Includes all nested calls. The first node in the list has no incoming edges.

         *     The last node in the list has no outgoing edges.

         */

                        List<GraphNode<?>> moved = extractMovables(iterator, newMarker);

                        connectAppend(res, moved);

                    } else if (newMarker.getCall().equals(callMarker.getCall())) {

                        if (res.isEmpty())

                            insertCallerNode(res, CallNode.Return.create(callMarker.getCall()), callMarker);

                        assert !res.isEmpty();

                        return res; // Process ended.

                    } else {

                        throw new IllegalStateException("Invalid pairing of call markers");