Non-fieldable payment method cannot work together

To simulate the problem:-
1. Enable non-fieldable payment method such as commerce_payment_example
2. Enable a fieldable payment method.
3. Change the payment method weight to make the fieldable payment method come before non-fieldable payment method at checkout form
4. At checkout form, select non-fieldable payment method and click next. The below error would come out.

Notice: Undefined index: transaction in commerce_payment_fields_commerce_payment_pane_checkout_form_validateblockquote) (line 58 of sites/all/modules/commerce_payment_fields/includes/commerce_payment_fields.checkout_pane.inc).
EntityMalformedException: Missing bundle property on entity of type commerce_payment_transaction. in entity_extract_ids() (line 7734 of /includes/common.inc).