[fix ]Test warnings

Author: i4004

src/Simplify.System.Tests/Extensions/ObservableCollectionExtensionsTests.cs

@@ -23,6 +23,8 @@ public void Null_Empty_Collections()
 
 			// Act & Assert
 
+#pragma warning disable CS8604
+
 			Assert.Catch(() => collection!.AddRange(items!), msg);
 			Assert.Catch(() => collection!.AddRange(items.AsEnumerable()), msg);
 			Assert.Catch(() => collection!.RefreshItems(items!), msg);
@@ -44,6 +46,8 @@ public void Null_Empty_Collections()
 			Assert.DoesNotThrow(() => collection.RefreshIndices(indices!), msg);
 			Assert.DoesNotThrow(() => collection.RefreshIndices(indices.AsEnumerable()), msg);
 
+#pragma warning restore CS8604
+
 			// Arrange
 
 			items = new object[] { };