Fix issue with Throttling and Scrolling in FilePicker component

Author: VictorRomanov1986

src/controls/filePicker/controls/FileBrowser/FileBrowser.tsx

@@ -507,15 +507,15 @@ export class FileBrowser extends React.Component<IFileBrowserProps, IFileBrowser
 
 
       // Remove the null mark from the end of the items array
-      if (concatenateResults && items && items.length > 0 && items.length[items.length - 1] === null) {
+      if (concatenateResults && items && items.length > 0 && items[items.length - 1] === null) {
         // Remove the null mark
         items.splice(items.length - 1, 1);
       }
       //concatenate results
       const newItems = concatenateResults ? items.concat(filesQueryResult.items) : filesQueryResult.items;
 
       // If there are more items to load -> add null mark at the end of the array
-      if (filesQueryResult.nextHref !== null) {
+      if (filesQueryResult.nextHref) {
         newItems.push(null);
       }
 

src/controls/filePicker/controls/TilesList/TilesList.tsx

@@ -61,14 +61,16 @@ export class TilesList extends React.Component<ITilesListProps> {
     return (
       <SelectionZone selection={this.props.selection} onItemInvoked={(item: IFile) => { this._handleItemInvoked(item); }}>
         <FocusZone>
-          <List
-            ref={(e: List) => { this._listElem = e; }}
-            className={styles.folderList}
-            items={this.props.items}
-            getItemCountForPage={this._getItemCountForPage}
-            getPageHeight={this._getPageHeight}
-            onRenderPage={(pageProps: IPageProps, defaultRender?: IRenderFunction<IPageProps>) => this._onRenderPage(pageProps, defaultRender)}
-          />
+          <div data-is-scrollable>
+            <List
+              ref={(e: List) => { this._listElem = e; }}
+              className={styles.folderList}
+              items={this.props.items}
+              getItemCountForPage={this._getItemCountForPage}
+              getPageHeight={this._getPageHeight}
+              onRenderPage={(pageProps: IPageProps, defaultRender?: IRenderFunction<IPageProps>) => this._onRenderPage(pageProps, defaultRender)}
+            />
+          </div>
         </FocusZone>
       </SelectionZone>
     );