fix(cdk/a11y): add parent node check to AriaDescriber (#19951)
fix(cdk/a11y): add parent node check to AriaDescriber (#19951)

Adds a check for `parentNode` when removing a description node in AriaDescriber.

Fixes #19949

andrewseguin/material2,angular/components,josephperrott/material2,mmalerba/material2,andrewseguin/material2,DevVersion/material2,angular/components,crisbeto/material2,DevVersion/material2,andrewseguin/material2,crisbeto/material2,mmalerba/material2,josephperrott/material2,josephperrott/material2,angular/components,mmalerba/material2,josephperrott/material2,mmalerba/material2,andrewseguin/material2,angular/components,DevVersion/material2,josephperrott/material2,DevVersion/material2,mmalerba/material2,crisbeto/material2,crisbeto/material2,DevVersion/material2,andrewseguin/material2