gulp error. The following tasks did not complete: default. How to fix?

Question

gulp.js

All good!
It costs smart-grid and gulp 4.0
I can't figure out why it gives an error
grid placed into ./source/style/common/smart-grid.less
Grid length is 21734 :)
Its work! good day!
[12:02:03] The following tasks did not complete: default
[12:02:03] Did you forget to signal async completion?

'use strict';

global.$ = {
    gulp: require('gulp'),
    smartgrid: require('smart-grid')
};
$.gulp.task('default',function () {
    return $.smartgrid('./source/style/common', {
        outputStyle: 'less', /* less || scss || sass || styl */
        columns: 12, /* number of grid columns */
        offset: "30px", /* gutter width px || % */
        container: {
            maxWidth: '1200px', /* max-width оn very large screen */
            fields: '30px' /* side fields */
        },
        breakPoints: {
            lg: {
                'width': '1100px', /* -> @media (max-width: 1100px) */
                'fields': '30px' /* side fields */
            },
            md: {
                'width': '960px',
                'fields': '15px'
            },
            sm: {
                'width': '780px',
                'fields': '15px'
            },
            xs: {
                'width': '560px',
                'fields': '15px'
            }
        }
    })
});