allow custom error when form does not use a model

This PR change the has_errors? method to allow
custom errors on forms without a model

lib/simple_form/components/errors.rb

@@ -11,7 +11,7 @@ def full_error(wrapper_options = nil)
       end
 
       def has_errors?
-        object && object.respond_to?(:errors) && errors.present?
+        object_with_errors? || object.nil? && has_custom_error?
       end
 
       def has_value?
@@ -34,6 +34,10 @@ def full_error_text
         has_custom_error? ? options[:error] : full_errors.send(error_method)
       end
 
+      def object_with_errors?
+        object && object.respond_to?(:errors) && errors.present?
+      end
+
       def error_method
         options[:error_method] || SimpleForm.error_method
       end

test/form_builder/error_test.rb

@@ -224,6 +224,12 @@ def with_full_error_for(object, *args)
     assert_no_select 'span.error'
   end
 
+  test 'input with custom error works when form does not use a model' do
+    with_form_for :user, :active, error: "Super User Active! cannot be blank"
+
+    assert_select 'span.error'
+  end
+
   test 'input with custom error works when using full_error component' do
     swap_wrapper :default, custom_wrapper_with_full_error do
       error_text = "Super User Name! cannot be blank"