message: Pass null version to get snapshot tree
diff: @@ -316,7 +316,7 @@ export class Container extends EventEmitter implements IContainer {
  // Get the snapshot tree
  const treeP = Promise.all([storageP, versionP]).then(
  - ([storage, version]) => version ? storage.getSnapshotTree(version) : null);
  + ([storage, version]) => storage.getSnapshotTree(version));
  const attributesP = Promise.all([storageP, treeP]).then<IDocumentAttributes>(
  ([storage, tree]) => {
  