fix(igxHierarchicalGrid): Fixing navigation when parent has summary b…

[MayaKirova]

…ut child does not.

Closes #4416

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code
• This PR includes API docs for newly added methods/properties
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes
• This PR includes behavioral changes and the feature specification has been updated with them

[mpavlinov]

@MayaKirova I found 2 problems:

Cannot read property 'childGridsData' of undefined

Steps

1. Expand "Ahmad Nazeri"
2. Focus "Kimmy McIlmorie"
3. Press Shift + Tab
4. Error is thrown

ERROR TypeError: Cannot read property 'childGridsData' of undefined
    at IgxHierarchicalGridComponent.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid.component.ts.IgxHierarchicalGridComponent.isChildGridRecord (hierarchical-grid.component.ts:535)
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.getIsChildAtIndex (hierarchical-grid-navigation.service.ts:54)
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.goToLastCell (hierarchical-grid-navigation.service.ts:193)
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.performShiftTabIntoChild (hierarchical-grid-navigation.service.ts:453)
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.performShiftTabKey (hierarchical-grid-navigation.service.ts:396)

Cannot read property 'length' of null

Steps

1. Expand "Alicia Stanger"
2. Focus "Peter Taylor"
3. Press Shift + Tab

IgxHierarchicalRowComponent.html:34 ERROR TypeError: Cannot read property 'length' of null
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.goToLastCell (hierarchical-grid-navigation.service.ts:192)
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.performShiftTabIntoChild (hierarchical-grid-navigation.service.ts:453)
    at IgxHierarchicalGridNavigationService.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-grid-navigation.service.ts.IgxHierarchicalGridNavigationService.performShiftTabKey (hierarchical-grid-navigation.service.ts:396)
    at IgxHierarchicalGridCellComponent.push../projects/igniteui-angular/src/lib/grids/cell.component.ts.IgxGridCellComponent.handleTab (cell.component.ts:768)
    at IgxHierarchicalGridCellComponent.push../projects/igniteui-angular/src/lib/grids/cell.component.ts.IgxGridCellComponent.dispatchEvent (cell.component.ts:845)
    at IgxHierarchicalGridCellComponent.push../projects/igniteui-angular/src/lib/grids/hierarchical-grid/hierarchical-cell.component.ts.IgxHierarchicalGridCellComponent.dispatchEvent (hierarchical-cell.component.ts:111)

Note: I couldn't reproduce those in 8.1.0