Merge pull request #7143 from unoplatform/mergify/bp/release/stable/3…

….10/pr-7132

fix(Android): Fix NRE when TextBlock.FontFamily is null (backport #7132)

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/Given_TextBlock.cs

@@ -1,9 +1,11 @@
 using System.Linq;
+using System.Threading.Tasks;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Windows.Foundation;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Documents;
+using static Private.Infrastructure.TestServices;
 
 namespace Uno.UI.RuntimeTests.Tests.Windows_UI_Xaml_Controls
 {
@@ -54,5 +56,14 @@ public void Check_Text_When_Having_Inline_Text_In_Span()
 			Assert.AreEqual("did", ((Run)((Italic)inlines[1]).Inlines.Single()).Text);
 			Assert.AreEqual(" my text go?", ((Run)inlines[2]).Text);
 		}
+
+		[TestMethod]
+		[RunsOnUIThread]
+		public async Task When_Null_FontFamily()
+		{
+			var SUT = new TextBlock { Text = "Some text", FontFamily = null };
+			WindowHelper.WindowContent = SUT;
+			SUT.Measure(new Size(1000, 1000));
+		}
 	}
 }

src/Uno.UI/UI/Xaml/Extensions/FontHelper.Android.cs

@@ -1,4 +1,6 @@
-using Android.App;
+#nullable enable
+
+using Android.App;
 using Android.Graphics;
 using System;
 using System.Collections.Generic;
@@ -20,9 +22,9 @@ internal partial class FontHelper
 		private static bool _assetsListed;
 		private static readonly string DefaultFontFamilyName = "sans-serif";
 
-		internal static Typeface FontFamilyToTypeFace(FontFamily fontFamily, FontWeight fontWeight, TypefaceStyle style = TypefaceStyle.Normal)
+		internal static Typeface? FontFamilyToTypeFace(FontFamily? fontFamily, FontWeight fontWeight, TypefaceStyle style = TypefaceStyle.Normal)
 		{  
-			var entry = new FontFamilyToTypeFaceDictionary.Entry(fontFamily.Source, fontWeight, style);
+			var entry = new FontFamilyToTypeFaceDictionary.Entry(fontFamily?.Source, fontWeight, style);
 
 			if (!_fontFamilyToTypeFaceDictionary.TryGetValue(entry , out var typeFace))
 			{
@@ -33,14 +35,14 @@ internal static Typeface FontFamilyToTypeFace(FontFamily fontFamily, FontWeight
 			return typeFace;
 		}
 
-		internal static Typeface InternalFontFamilyToTypeFace(FontFamily fontFamily, FontWeight fontWeight, TypefaceStyle style)
+		internal static Typeface? InternalFontFamilyToTypeFace(FontFamily? fontFamily, FontWeight fontWeight, TypefaceStyle style)
 		{
 			if (fontFamily?.Source == null || fontFamily.Equals(FontFamily.Default))
 			{
 				fontFamily = GetDefaultFontFamily(fontWeight);
 			}
 
-			Typeface typeface;
+			Typeface? typeface;
 
 			try
 			{
@@ -72,7 +74,7 @@ internal static Typeface InternalFontFamilyToTypeFace(FontFamily fontFamily, Fon
 					{
 						typeface = Android.Graphics.Typeface.CreateFromAsset(Android.App.Application.Context.Assets, actualAsset);
 
-						if (style != typeface.Style)
+						if (style != typeface?.Style)
 						{
 							typeface = Typeface.Create(typeface, style);
 						}

src/Uno.UI/UI/Xaml/Extensions/FontHelper.Lookup.Android.cs

@@ -1,4 +1,6 @@
-using Android.App;
+#nullable enable
+
+using Android.App;
 using Android.Graphics;
 using System;
 using System.Collections.Generic;
@@ -26,19 +28,19 @@ public class Entry
 			{
 				private readonly int _hashCode;
 
-				public Entry(string fontFamily, FontWeight fontWeight, TypefaceStyle style)
+				public Entry(string? fontFamily, FontWeight fontWeight, TypefaceStyle style)
 				{
 					FontFamily = fontFamily;
 					FontWeight = fontWeight;
 					Style = style;
-					_hashCode = FontFamily.GetHashCode() ^ FontWeight.GetHashCode() ^ Style.GetHashCode();
+					_hashCode = (FontFamily?.GetHashCode() ?? 0) ^ FontWeight.GetHashCode() ^ Style.GetHashCode();
 				}
 
-				public string FontFamily { get; }
+				public string? FontFamily { get; }
 				public FontWeight FontWeight { get; }
 				public TypefaceStyle Style { get; }
 
-				public override bool Equals(object other)
+				public override bool Equals(object? other)
 				{
 					if (other is Entry otherEntry)
 					{
@@ -55,19 +57,19 @@ public override bool Equals(object other)
 
 			private readonly HashtableEx _entries = new HashtableEx();
 
-			internal bool TryGetValue(Entry key, out Typeface result)
+			internal bool TryGetValue(Entry key, out Typeface? result)
 			{
 				if (_entries.TryGetValue(key, out var value))
 				{
-					result = (Typeface)value;
+					result = (Typeface?)value;
 					return true;
 				}
 
 				result = null;
 				return false;
 			}
 
-			internal void Add(Entry key, Typeface typeFace)
+			internal void Add(Entry key, Typeface? typeFace)
 				=> _entries.Add(key, typeFace);
 
 			internal void Clear()