Wrap EmptyStatePanel in a Card for consistency

This fixes two issues, the "No such file or directory" view now shows
the EmptyStatePanel properly centered and with the expected background
colour. (The same background colour as the normal folder view.

Closes: #568

src/app.tsx

@@ -22,6 +22,7 @@ import React, { useContext, useEffect, useMemo, useState } from "react";
 import {
     AlertGroup, Alert, AlertVariant, AlertActionCloseButton
 } from "@patternfly/react-core/dist/esm/components/Alert";
+import { Card } from "@patternfly/react-core/dist/esm/components/Card";
 import { Page, PageSection } from "@patternfly/react-core/dist/esm/components/Page";
 import { Sidebar, SidebarPanel, SidebarContent } from "@patternfly/react-core/dist/esm/components/Sidebar";
 import { ExclamationCircleIcon } from "@patternfly/react-icons";
@@ -166,10 +167,12 @@ export const Application = () => {
                         <Sidebar isPanelRight hasGutter>
                             <SidebarContent>
                                 {errorMessage &&
-                                <EmptyStatePanel
-                                  paragraph={errorMessage}
-                                  icon={ExclamationCircleIcon}
-                                />}
+                                <Card>
+                                    <EmptyStatePanel
+                                      paragraph={errorMessage}
+                                      icon={ExclamationCircleIcon}
+                                    />
+                                </Card>}
                                 {!errorMessage &&
                                 <FilesFolderView
                                   path={path}