Remove reference to undefined variable

[braders]

Overview

In CRM_Price_BAO_PriceFieldValue::add, $fieldValueBAO->id was read before $fieldValueBAO is defined; this can obviously not work.

The variable was defined prior to commit 50a890f 2 years ago, which swapped the order of operations. This change restores the original order of operations, but ensures that the default is set correctly. See #17960 for more context for the original problem from 2 years prior.

This only impacts extensions which might be using CRM_Price_BAO_PriceFieldValue; core calls to CRM_Price_BAO_PriceFieldValue::add always pass in the price_field_id meaning the faulty code was never reached.

[civibot]

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[demeritcowboy]

Thanks @braders. It's interesting that core would always pass price_field_id since I would guess the use-case for it being missing would be contribution page amounts with no explicit price sets (quick_config magic price set), but it must take the "slow" route.