fix parsing 'null' in the state.

Author: endel

Assets/Plugins/Colyseus/DeltaListener/Compare.cs

@@ -53,7 +53,12 @@ protected static void Generate(IndexedDictionary<string, object> mirror, Indexed
 			for (int i = 0; i < oldKeys.Count; i++) 
 			{
 				var key = oldKeys [i];
-				if (obj.ContainsKey(key) && !(!obj.ContainsKey(key) && mirror.ContainsKey(key) && !(obj is List<object>)))
+				if (
+					obj.ContainsKey(key) && 
+					obj[key] != null &&
+					!(!obj.ContainsKey(key) && mirror.ContainsKey(key) && 
+					!(obj is List<object>))
+				)
 				{
 					var oldVal = mirror[key];
 					var newVal = obj[key];

Assets/Tests/DeltaContainerTest.cs

@@ -36,6 +36,22 @@ public void ListenAddString() {
 		Assert.AreEqual (1, listenCalls);
 	}
 
+	[Test]
+	public void ListenAddNull() {
+		var newData = GetRawData ();
+		newData ["null_new"] = null;
+
+		var listenCalls = 0;
+		container.Listen ("null_new", (DataChange change) => {
+			listenCalls++;
+			Assert.AreEqual("add", change.operation);
+			Assert.AreEqual(null, change.value);
+		});
+
+		container.Set (newData);
+		Assert.AreEqual (1, listenCalls);
+	}
+
 	[Test]
 	public void ListenAddRemove() {
 		var newData = GetRawData ();
@@ -198,6 +214,7 @@ protected IndexedDictionary<string, object> GetRawData () {
 		}));
 		data.Add ("players", players);
 		data.Add ("turn", "none");
+		data.Add ("null", null);
 		data.Add ("messages", new List<object> { "one", "two", "three" });
 		return data;
 	}