How to get terms from a custom taxonomies after WordPress 4.5.0

OK, wild guess:

$prefix_topic_terms= array();
if ( ! empty( $iva_topic_terms ) ) {

vs

$prefix_topic_terms = array();
if ( ! empty( $prefix_topic_terms ) ) {

You’ve changed the variable that is checked for emptiness in the new code. That code will never query get_terms for that taxonomy, because $prefix_topic_terms will not be empty.
The Error-object you are receiving is probably unrelated from an earlier call to get_terms.

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