Check style.Ignore if style is not null.

[Rosuavio]

Fixes #4116

Style could have been null on the check for style.Ignore, moved the
check so it cant be null.

In the SampleApp there are docs that we render that have the markdown syntax

> Hello world

And should be rendered as

Hello world

The issues is our code that checks for special quotes with special style tags like [!NOTE] or [!TIP] does not handle there not being one of those style tags at the beginning of the quote and the example code would crash the rendered. This change no longer checks style.Ignore if the style tag is not in our dictionary.

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

Markdown quotes that don't start with a style tag cash the sample app.

What is the new behavior?

Markdown quotes that don't start with a style tag don't get checked if there non-existing style's Ignore prop is true.

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information

How it looks now

Source https://github.com/MicrosoftDocs/WindowsCommunityToolkitDocs/blob/a70069e9d133b677507e37f526eadc08299202b5/docs/graph/controls/PersonView.md

[ghost]

Thanks RosarioPulella for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

[ghost]

Hello @michael-hawker!

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[michael-hawker]

@XAML-Knight mind testing this out quick too, should be pretty straight-forward?

I'm pretty sure this just effects the sample app and not the markdown control itself.