Solve the issue where the bottom view of Sidebar was pushed down

Summary: This fixes the issue raised [here](https://fb.workplace.com/groups/flippersupport/permalink/911822855965040/).

Reviewed By: nikoant

Differential Revision: D22411617

fbshipit-source-id: ca1078bf418532863823fb3748e9edea4526cbc2

desktop/app/src/App.tsx

@@ -65,7 +65,7 @@ type DispatchProps = {
   setActiveSheet: typeof setActiveSheet;
 };
 
-const MainContent = styled(FlexRow)({
+const MainContent = styled(FlexColumn)({
   height: 'calc(100vh - 38px)',
 });
 
@@ -154,10 +154,11 @@ export class App extends React.Component<Props> {
     return (
       <FlexColumn grow={true}>
         <TitleBar version={version} />
-        <DoctorBar />
-        <ErrorBar />
         <Sheet>{this.getSheet}</Sheet>
         <MainContent>
+          <DoctorBar />
+          <ErrorBar />
+          <FlexRow grow scrollable>
             {this.props.leftSidebarVisible && <MainSidebar2 />}
             <PluginContent>
               {this.props.staticView != null ? (
@@ -179,6 +180,7 @@ export class App extends React.Component<Props> {
                 }}
               />
             </PluginContent>
+          </FlexRow>
         </MainContent>
         <StatusBar />
       </FlexColumn>