dev/drupal#148 Fix product form such that it is possible to unseletc …

[eileenmcnaughton]

…duration unit, frequency unit

Overview

Fixes a regression from buttonrama whereby some fields on the premiums form inadvertantly became 'required'

Before

Cannot create a premium with entering duration & frequency

After

The duration_unit & frequency unit are converted to use addField (select 2) and no longer default to / require a value

Technical Details

I thought about converting more fields to use addField but it requires extra schema data to be defined (html) so not rc-suitable

Comments

[civibot]

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[seamuslee001]

@eileenmcnaughton style issue https://test.civicrm.org/job/CiviCRM-Core-PR/38155/checkstyleResult/new/

[seamuslee001]

Submitter reports it works for them and code looks fine to me MOP