The following code in bug_report.php may be wrong

# Validate the custom fields before adding the bug.
$t_related_custom_field_ids = custom_field_get_linked_ids( $t_bug_data->project_id );
foreach( $t_related_custom_field_ids as $t_id ) {
    $t_def = custom_field_get_definition( $t_id );

    # Produce an error if the field is required but wasn't posted
    if ( !gpc_isset_custom_field( $t_id, $t_def['type'] ) &&
        ( $t_def['require_report'] ||
            $t_def['type'] == CUSTOM_FIELD_TYPE_ENUM ||
            $t_def['type'] == CUSTOM_FIELD_TYPE_LIST ||
            $t_def['type'] == CUSTOM_FIELD_TYPE_MULTILIST ||
            $t_def['type'] == CUSTOM_FIELD_TYPE_RADIO ) ) {
        error_parameters( lang_get_defaulted( custom_field_get_field( $t_id, 'name' ) ) );
        trigger_error( ERROR_EMPTY_FIELD, ERROR );
    }
    if ( !custom_field_validate( $t_id, gpc_get_custom_field( "custom_field_$t_id", $t_def['type'], NULL ) ){
        error_parameters( lang_get_defaulted( custom_field_get_field( $t_id, 'name' ) ) );
        trigger_error( ERROR_CUSTOM_FIELD_INVALID_VALUE, ERROR );
    }
}