function create_data_node(node, previous) {
	if (node?.type === 'data') return node;
	if (node?.type === 'skip') return previous ?? null;
	return null;
}
@param {import('types').ServerDataNode | import('types').ServerDataSkippedNode | null} node
@param {import('./types.js').DataNode | null} [previous]
@returns {import('./types.js').DataNode | null}