Dashboard: When dashboard is not found show message instead of empty page (#65508)

* setup page when dashboard is not found

* reuse ErrorPage for not found dashboard

public/app/features/dashboard/containers/DashboardPage.tsx

@@ -19,6 +19,7 @@ import { selectors } from '@grafana/e2e-selectors';
 import { config, locationService } from '@grafana/runtime';
 import { Icon, Themeable2, withTheme2 } from '@grafana/ui';
 import { notifyApp } from 'app/core/actions';
+import ErrorPage from 'app/core/components/ErrorPage/ErrorPage';
 import { Page } from 'app/core/components/Page/Page';
 import { GrafanaContext, GrafanaContextType } from 'app/core/context/GrafanaContext';
 import { createErrorNotification } from 'app/core/copy/appNotification';
@@ -440,6 +441,10 @@ export class UnthemedDashboardPage extends PureComponent<Props, State> {
         >
           <DashboardPrompt dashboard={dashboard} />
           {initError && <DashboardFailed />}
+          {dashboard.meta.dashboardNotFound ? (
+            <ErrorPage />
+          ) : (
+            <>
               {showSubMenu && (
                 <section aria-label={selectors.pages.Dashboard.SubMenu.submenu}>
                   <SubMenu dashboard={dashboard} annotations={dashboard.annotations.list} links={dashboard.links} />
@@ -481,6 +486,8 @@ export class UnthemedDashboardPage extends PureComponent<Props, State> {
                 />
               )}
               {inspectPanel && <PanelInspector dashboard={dashboard} panel={inspectPanel} />}
+            </>
+          )}
         </Page>
         {editPanel && (
           <PanelEditor