Fix display of premiums on contribution pages
PR Ref: https://github.com/civicrm/civicrm-core/pull/12437
If a premium product is created with no financial type and then added to a contribution page it is not displayed because the contribution page is only selecting those with a financial type, but financial type is optional unless you have configured a cost for the product.
Furthermore, if you update the premium product to have a financial type that is not mirrored to the civicrm_premium_product table which contains the configuration for the premium products available on a contribution page.