Use constant NIL in lib "uuid"

Signed-off-by: Franck LECUYER <[email protected]>

Author: FranckLecuyer

src/components/app.test.tsx

@@ -14,8 +14,9 @@ import { createTheme, CssBaseline, StyledEngineProvider, ThemeProvider } from '@
 import { SnackbarProvider } from '@gridsuite/commons-ui';
 import { store } from '../redux/store';
 import App from './app';
+import { NIL as NIL_UUID } from 'uuid';
 
-jest.mock('uuid', () => ({ v4: () => '00000000-0000-0000-0000-000000000000' }));
+jest.mock('uuid', () => ({ v4: () => NIL_UUID }));
 
 let container: HTMLDivElement | null = null;
 beforeEach(() => {

src/components/tree.test.ts

@@ -7,8 +7,9 @@
 
 import { ElementType } from '@gridsuite/commons-ui';
 import { updatedTree } from './treeview-utils';
+import { NIL as NIL_UUID } from 'uuid';
 
-jest.mock('uuid', () => ({ v4: () => '00000000-0000-0000-0000-000000000000' }));
+jest.mock('uuid', () => ({ v4: () => NIL_UUID }));
 
 const otherProperties = {
     description: 'desc',