serv4 + submodule update (#12740)

Co-authored-by: DrSmugleaf <DrSmugleaf@users.noreply.github.com>

Content.IntegrationTests/Tests/Chemistry/FixedPoint2SerializationTest.cs

@@ -18,16 +18,31 @@ namespace Content.IntegrationTests.Tests.Chemistry
         [Test]
         public void DeserializeNullTest()
         {
-            var node = new ValueDataNode("null");
+            var node = ValueDataNode.Null();
             var unit = Serialization.Read<FixedPoint2?>(node);
 
             Assert.That(unit, Is.Null);
         }
 
+        [Test]
+        public void SerializeNullTest()
+        {
+            var node = Serialization.WriteValue<FixedPoint2?>(null);
+            Assert.That(node.IsNull);
+        }
+
+        [Test]
+        public void SerializeNullableValueTest()
+        {
+            var node = Serialization.WriteValue<FixedPoint2?>(FixedPoint2.New(2.5f));
+            Assert.That(node is ValueDataNode);
+            Assert.That(((ValueDataNode)node).Value, Is.EqualTo("2.5"));
+        }
+
         [Test]
         public void DeserializeNullDefinitionTest()
         {
-            var node = new MappingDataNode().Add("unit", "null");
+            var node = new MappingDataNode().Add("unit", ValueDataNode.Null());
             var definition = Serialization.Read<FixedPoint2TestDefinition>(node);
 
             Assert.That(definition.Unit, Is.Null);