Pressing Down Arrow while summaries are focused throws an error in igxHierarchicalGrid

[mpavlinov]

Description

Describe the issue.

• igniteui-angular version: 8.1.0
• browser: *

Steps to reproduce

1. Open https://www.infragistics.com/products/ignite-ui-angular/angular/components/hierarchicalgrid/summaries.html#demo
2. Expand "Naomí Yepes"
3. Focus the summary for the albums of "Naomi Yepes"
4. Press the Arrow Down
5. Observe the console

Result

ERROR TypeError: Cannot read property 'nodeName' of undefined
    at Ya.navigateDown (main-es2015.2f33516b7918564c0b45.js:1)
    at Object.dispatchEvent (main-es2015.2f33516b7918564c0b45.js:1)
    at Object.handleEvent (main-es2015.2f33516b7918564c0b45.js:1)
    at Object.handleEvent (main-es2015.2f33516b7918564c0b45.js:1)
    at Object.handleEvent (main-es2015.2f33516b7918564c0b45.js:1)
    at Yr (main-es2015.2f33516b7918564c0b45.js:1)
    at main-es2015.2f33516b7918564c0b45.js:1
    at HTMLElement.<anonymous> (main-es2015.2f33516b7918564c0b45.js:1)
    at a.invokeTask (polyfills-es2015.3dd86396238f413fd411.js:1)
    at Object.onInvokeTask (main-es2015.2f33516b7918564c0b45.js:1)

Expected result

There should be no error