[iOS/MacCatalyst] Fix CheckBox foreground color not resetting when set to null

src/Core/src/Platform/iOS/CheckBoxExtensions.cs

@@ -16,6 +16,11 @@ public static void UpdateForeground(this MauiCheckBox platformCheckBox, ICheckBo
 			{
 				platformCheckBox.CheckBoxTintColor = solid.Color;
 			}
+			else if (check.Foreground is null)
+			{
+				// Color was cleared; reset to null so the view inherits the default tint color
+				platformCheckBox.CheckBoxTintColor = null;
+			}
 		}
 	}
 }

src/Core/tests/DeviceTests/Handlers/CheckBox/CheckBoxHandlerTests.iOS.cs

@@ -64,5 +64,31 @@ async Task ValidateColor(ICheckBox checkBoxStub, Color color, Action action = nu
 			});
 			Assert.Equal(expected, color);
 		}
+
+		[Fact(DisplayName = "Foreground Resets to Default When Set to Null")]
+		public async Task ForegroundResetsToDefaultWhenSetToNull()
+		{
+			var checkBoxStub = new CheckBoxStub
+			{
+				Foreground = new SolidPaint(Colors.Red),
+				IsChecked = true
+			};
+
+			await InvokeOnMainThreadAsync(() =>
+			{
+				var handler = CreateHandler(checkBoxStub);
+				var native = GetNativeCheckBox(handler);
+
+				// Confirm that the red tint was applied initially
+				Assert.NotNull(native.CheckBoxTintColor);
+
+				// Simulate a dynamic Color = null (Foreground reset to default)
+				checkBoxStub.Foreground = null;
+				handler.UpdateValue(nameof(ICheckBox.Foreground));
+
+				// After reset, the native tint must be null so iOS reverts to its inherited default
+				Assert.Null(native.CheckBoxTintColor);
+			});
+		}
 	}
 }