Fix: return default WP meta behavior for GiveWP types (#7062)

Co-authored-by: Jason Adams <[email protected]>

includes/database/class-give-db-meta.php

@@ -126,7 +126,7 @@ function __construct() {
 	/**
 	 * Retrieve payment meta field for a payment.
 	 *
-	 * @access  public
+	 * @unreleased Return empty array, when request raw metadata if $single is set to false and metadata does not exist.
 	 * @since   2.0
 	 *
 	 * @param   int    $id       Pst Type  ID.
@@ -150,7 +150,7 @@ public function get_meta( $id = 0, $meta_key = '', $single = false ) {
 
 		if ( $this->raw_result ) {
 			if ( ! ( $value = get_metadata( $this->meta_type, $id, $meta_key, false ) ) ) {
-				$value = '';
+				$value = $single ? '' : array();
 			}
 
 			// Reset flag.