StyleDeclarationExtensions.GetColor throws when there is no color assigned

[Shayan-To]

Prerequisites

• Can you reproduce the problem in a MWE?
• Are you running the latest version of AngleSharp.Css?
• Did you check the FAQs to see if that helps you?
• Are you reporting to the correct repository? (there are multiple AngleSharp libraries, e.g., AngleSharp.Xml for Xml support)
• Did you perform a search in the issues?

Description

I want to extract text and style from an html document, but when I try to use element.ComputeCurrentStyle().GetColor(), it throws an exception.

Steps to Reproduce

    using var angle = AngleSharp.BrowsingContext.New();
    var parser = angle.GetService<IHtmlParser>()!;

    using var doc = await parser.ParseDocumentAsync("<div>hi</div>");

    Console.WriteLine(doc.QuerySelector("div").ComputeCurrentStyle().GetColor());

Expected Behavior

Outputs null or a default color.

Actual Behavior

AngleSharp.Css.Dom.CssStyleDeclaration
System.InvalidOperationException: Sequence contains no elements
   at System.Linq.ThrowHelper.ThrowNoElementsException()
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at AngleSharp.BrowsingContextExtensions.GetFactory[TFactory](IBrowsingContext context)
   at AngleSharp.Css.Dom.CssStyleDeclaration.TryCreateShorthand(String shorthandName, IEnumerable`1 serialized, List`1 usedProperties, Boolean force)
   at AngleSharp.Css.Dom.CssStyleDeclaration.GetPropertyShorthand(String name)
   at AngleSharp.Css.Dom.CssStyleDeclaration.GetProperty(String name)
   at AngleSharp.Css.Dom.CssStyleDeclaration.GetPropertyValue(String propertyName)
   at AngleSharp.Css.Dom.StyleDeclarationExtensions.GetColor(ICssStyleDeclaration style)

Possible Solution / Known Workarounds

Is there a way to assign a default color to the document so it can fall back to it when no color is assigned to the elements?
Is there a way to have some browser default styles be loaded? Even manually?