fix(radio-button): Cannot read property 'nodeName' of null

[Splaktar]

PR Checklist

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• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Some users see TypeError: Cannot read property 'nodeName' of null when on a page with a md-radio-button after they hit the browser's reload button, since AngularJS Material 1.1.1.

Issue Number:
Fixes #10546

What is the new behavior?

There is a null check before accessing the parentNode field.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

No test added as no reproduction was provided.