Fix error with deserialization of property data types that may contain null values (#1073)

Author: claudiamurialdo

dotnet/src/dotnetframework/GxClasses/Domain/GxCollections.cs

@@ -2400,7 +2400,8 @@ public void FromJSONObject(dynamic obj)
 				{
 					lock (syncObj)
 					{
-						this.Set(item.Key.ToString(), item.Value.ToString());
+						if (item.Key != null && item.Value != null)
+							this.Set(item.Key.ToString(), item.Value.ToString());
 					}
 				}
 			}