Support null values in NumericValidationBehavior

Author: reck1610

src/CommunityToolkit.Maui.UnitTests/Behaviors/NumericValidationBehaviorTests.cs

@@ -85,8 +85,12 @@ public async Task IsNull()
 			Text = text
 		};
 		entry.Behaviors.Add(behavior);
+		
+		//Act
+		await behavior.ForceValidate(TestContext.Current.CancellationToken);
 
-		await Assert.ThrowsAsync<ArgumentNullException>(async () => await behavior.ForceValidate(TestContext.Current.CancellationToken));
+		// Assert
+		Assert.False(behavior.IsValid);
 	}
 
 	[Fact(Timeout = (int)TestDuration.Short)]

src/CommunityToolkit.Maui/Behaviors/Validators/NumericValidationBehavior.shared.cs

@@ -76,8 +76,6 @@ public int MaximumDecimalPlaces
 	/// <inheritdoc/>
 	protected override ValueTask<bool> ValidateAsync(string? value, CancellationToken token)
 	{
-		ArgumentNullException.ThrowIfNull(value);
-
 		if (!(double.TryParse(value, out var numeric)
 			&& numeric >= MinimumValue
 			&& numeric <= MaximumValue))