Gulp sourcemaps Path must be a string error. How to treat?

Question

gulp.js

Gulp crashes when including sourcemaps. I have already tried everything: I reinstalled the packages, and tried to update the node package 'source-map'. Nothing helped, I decided to ask here. Has anyone come across something similar? How to cure it?
Here gulpfile.js:

'use strict';

const gulp = require('gulp');
const stylus = require('gulp-stylus');
const sourcemaps = require('gulp-sourcemaps');
const del = require('del');

const isDevelopment = !process.env.NODE_ENV || process.env.NODE_ENV == 'development';

gulp.task('styles', function() {

  return gulp.src('frontend/styles/main.styl')
      .pipe( sourcemaps.init())
      .pipe(stylus())
      .pipe(sourcemaps.write())
      .pipe(gulp.dest('public'));

});

gulp.task('clean', function() {
  return del('public');
});

gulp.task('assets', function() {
  return gulp.src('frontend/assets/**')
      .pipe(gulp.dest('public'));
});


gulp.task('build', gulp.series(
    'clean',
    gulp.parallel('styles', 'assets'))
);

Here is the error:

test:$> gulp build

> [email protected] gulp /Users/alex/projects/test
> gulp "build"

[18:34:27] Using gulpfile ~/projects/test/gulpfile.js
[18:34:27] Starting 'build'...
[18:34:27] Starting 'clean'...
[18:34:27] Finished 'clean' after 10 ms
[18:34:27] Starting 'styles'...
[18:34:27] Starting 'assets'...
[18:34:27] 'styles' errored after 185 ms
[18:34:27] TypeError in plugin 'gulp-stylus'
Message:
    /Users/alex/projects/test/frontend/styles/main.styl:8:1
   4|   margin 0
   5|   padding 0
   6|   width 100%
   7|   height 100%
   8|
------^

Path must be a string. Received undefined

Details:
    domainEmitter: [object Object]
    domain: [object Object]
    domainThrown: false
[18:34:27] 'build' errored after 200 ms
[18:34:27] The following tasks did not complete: assets

Here are the versions:

node v6.2.1
npm  v3.9.3
test:$> npm view gulp-sourcemaps version
1.6.0
test:$> npm view source-map version
0.5.6
test:$> npm view gulp-stylus version
2.4.0
test:$> npm view stylus version
0.54.5

Moreover, if you comment out .pipe(gulpIf(isDevelopment, sourcemaps.init())), then everything works. Only sourcemaps, of course, is not written.

Answer 1

.pipe(sourcemaps.write(''))
try to give the string as requested