diff --git a/src/containers/transform/MarkdownTreeProcessor.ts b/src/containers/transform/MarkdownTreeProcessor.ts
index e5ba87c5..b61408dc 100644
--- a/src/containers/transform/MarkdownTreeProcessor.ts
+++ b/src/containers/transform/MarkdownTreeProcessor.ts
@@ -1,12 +1,12 @@
-import {FileContentService} from '../../utils/FileContentService';
-import {TreeItem} from '../../model/TreeItem';
-import {DirectoryScanner, RESERVED_NAMES} from './DirectoryScanner';
-import {MimeTypes} from '../../model/GoogleFile';
-import {FileId} from '../../model/model';
+import { FileContentService } from '../../utils/FileContentService';
+import { TreeItem } from '../../model/TreeItem';
+import { DirectoryScanner, RESERVED_NAMES } from './DirectoryScanner';
+import { MimeTypes } from '../../model/GoogleFile';
+import { FileId } from '../../model/model';
 
 type CallBack<K> = (treeItem: K) => boolean;
 
-export type TreeItemTuple = [ TreeItem?, string? ];
+export type TreeItemTuple = [TreeItem?, string?];
 
 export class MarkdownTreeProcessor {
   private driveTree: TreeItem[] = [];
@@ -91,7 +91,7 @@ export class MarkdownTreeProcessor {
     for (const file of children) {
       const part = file['realFileName'];
       if (callBack(file)) {
-        return [ file, curPath ? curPath + '/' + part : part ];
+        return [file, curPath ? curPath + '/' + part : part];
       }
     }
 
@@ -142,6 +142,6 @@ export class MarkdownTreeProcessor {
       return null;
     }
 
-    return this.driveTree[0]['wikigdrive'];
+    return this.driveTree[0]['wikigdrive'] || null;
   }
 }