Fix passing nil to CSharp functions not returning function

Upsilon/BaseTypes/UserData/UpsilonBinder.cs

@@ -82,6 +82,11 @@ namespace Upsilon.BaseTypes.UserData
                             continue;
                     }
 
+                    if (argumentType == typeof(ScriptNull))
+                    {
+                        continue;
+                    }
+
                     if (!matchParameter.ParameterType.IsAssignableFrom(argumentType))
                     {
                         validMatch = false;
@@ -144,6 +149,10 @@ namespace Upsilon.BaseTypes.UserData
                     break;
             }
 
+            if (value is ScriptNull)
+            {
+                return null;
+            }
 
             var isScriptTypeRequired = typeof(ScriptType).IsAssignableFrom(type);
             var isScriptType = value is ScriptType;