Field Validation fails after update

I have this code snippet to validate WC fields.

add_filter( 'woocommerce_add_to_cart_validation', 'validate_fields', 1, 3 );
function validate_fields( $passed, $product_id, $pid = null) {
  	global $woocommerce;

	if( isset( $pid ) ) {
		$all_fields = apply_filters( 'wcff/load/all_fields', $product_id );
		foreach ( $all_fields as $fields ) {
			foreach ( $fields as $field ) {
				// my validation code here
			}
		}
	}
	return $passed;
}

It use to work fine but after updating to Version 2.0.6 I get the following error message:

Warning: Invalid argument supplied for foreach() in...

Did anything change in the API that would explain this?