Test alternate psych struct fix

lib/delayed/psych_ext.rb

@@ -136,6 +136,8 @@ def visit_Psych_Nodes_Mapping_with_class(object) # rubocop:disable CyclomaticCom
       alias_method_chain :visit_Psych_Nodes_Mapping, :class
 
       def resolve_class_with_constantize(klass_name)
+        return resolve_class_without_constantize(klass_name) if klass_name.blank?
+
         klass_name.constantize
       rescue
         resolve_class_without_constantize(klass_name)

spec/yaml_ext_spec.rb

@@ -22,6 +22,13 @@
     end.not_to raise_error
   end
 
+  it 'autoloads the class of an anonymous struct' do
+    yaml = "--- !ruby/struct\nn: 1\n"
+    object = YAML.load(yaml)
+    expect(object).to be_kind_of(Struct)
+    expect(object.n).to eq(1)
+  end
+
   it 'autoloads the class for the instance' do
     expect do
       yaml = "--- !ruby/object:Autoloaded::InstanceClazz {}\n"