message: Fix Page theme
diff: import _get from 'lodash/get';
  export default (overrides: any) => ({
  - ..._get(overrides, 'Page', {}),
  collapseBreakpoint: 'desktop',
  WithSidebar: {
  - sidebarWidth: '250px'
  - }
  + sidebarWidth: '250px',
  + ..._get(overrides, 'Page.WithSidebar', {})
  + },
  + ..._get(overrides, 'Page', {})
  });
  