IDL: Use Nullable for union type return value

Source/bindings/templates/methods.cpp

Index: Source/bindings/templates/methods.cpp
diff --git a/Source/bindings/templates/methods.cpp b/Source/bindings/templates/methods.cpp
index cf307e68859e6f8a5be32b7564636cd4045ddcad..0c3a4e07bd04e8226bebd6aceafa345168dffbdf 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -297,7 +297,6 @@ if (info.Length() >= 2 && listener && !impl->toNode())
 {######################################}
 {% macro union_type_method_call_and_set_return_value(method) %}
 {% for cpp_type in method.cpp_type %}
-bool result{{loop.index0}}Enabled = false;
 {{cpp_type}} result{{loop.index0}};
 {% endfor %}
 {{method.cpp_value}};
@@ -306,7 +305,7 @@ if ({{method.is_null_expression}})
     return;
 {% endif %}
 {% for v8_set_return_value in method.v8_set_return_value %}
-if (result{{loop.index0}}Enabled) {
+if (!result{{loop.index0}}.isNull()) {
     {{v8_set_return_value}};
     return;
 }