error on gulp

[Trabontea]

Hello!
I have this error on gulp

events.js:183
throw er; // Unhandled 'error' event
^
Error: Path must be a string. Received undefined
at Function.pleeease.process (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\pleeease\lib\pleeease.js:192:11)
at DestroyableTransform._transform (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\gulp-pleeease\index.js:32:29)
at DestroyableTransform.Transform._read (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\gulp-pleeease\node_modules\readable-stream\lib_stream_transform.js:184:10)
at DestroyableTransform.Transform._write (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\gulp-pleeease\node_modules\readable-stream\lib_stream_transform.js:172:12)
at doWrite (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\gulp-pleeease\node_modules\readable-stream\lib_stream_writable.js:237:10)
at writeOrBuffer (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\gulp-pleeease\node_modules\readable-stream\lib_stream_writable.js:227:5)
at DestroyableTransform.Writable.write (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\gulp-pleeease\node_modules\readable-stream\lib_stream_writable.js:194:11)
at DestroyableTransform.ondata (D:\WEB\LEARN\improve-gulpjs\mysite02\node_modules\through2\node_modules\readable-stream\lib_stream_readable.js:619:20)
at emitOne (events.js:116:13)

my gulpfile.js
`
var
gulp = require('gulp'),
newer = require('gulp-newer'),
preprocess = require('gulp-preprocess'),
htmlclean = require('gulp-htmlclean'),
imagemin = require('gulp-imagemin'),

sass = require('gulp-sass'),
pleeease = require('gulp-pleeease'),
jshint = require('gulp-jshint'),
size = require('gulp-size'),
del = require('del'),
concat= require('gulp-concat'),
deporder = require('gulp-deporder'),
stripdebug = require('gulp-strip-debug'),
uglify = require('gulp-uglify'),
browserSync = require('browser-sync'),
pkg = require('./package.json');

var
devBuild = ((process.env.NODE_ENV || 'development').trim().toLowerCase() !== 'production'),

source = 'source/',
dest = 'build/',

html = {
    in: source + '*.html',
    watch: [source + '*.html', source + 'template/**/*'],
    out: dest,
    context: {
        devBuild: devBuild,
        author: pkg.author,
        version: pkg.version
    }
},

images = {
	in: source + 'images/*.*',
	out: dest + 'images/'
},



css = {
    in: source + 'scss/main.scss',
    watch: [source + 'scss/**/*'],
    out: dest + 'css/',
    sassOpts: {
        outputStyle: 'nested',
        imagePath: '../images',
        precision: 3,
        errLogToConsole: true
    },
    pleeeaseOpts: {
        autoprefixer: { browsers: ['last 2 versions', '> 2%'] },
        rem: ['16px'],
        pseudoElements: true,
        mqpacker: true,
        minifier: !devBuild
    }
},

fonts = {
	in: source + 'fonts/*.*',
	out: css.out + 'fonts/'
},

js = {
    in: source + 'js/**/*',
    out: dest + 'js/',
    filename: 'main.js'
};

syncOpts = {
    server: {
        baseDir: dest,
        index: 'index.html'
    },
    open: false,
    notify: true
};

console.log(pkg.name + ' ' + pkg.version + ', ' + (devBuild ? 'development' : 'production') + ' build');

gulp.task('clean', function() {
del([
dest + '*'
]);
});

gulp.task('html', function() {
var page = gulp.src(html.in).pipe(preprocess({ context: html.context }));
if (!devBuild) {
page = page
.pipe(size({ title: 'HTML in' }))
.pipe(htmlclean())
.pipe(size({ title: 'HTML out' }));
}
return page.pipe(gulp.dest(html.out));
});

gulp.task('images', function() {
return gulp.src(images.in)
.pipe(newer(images.out))
.pipe(imagemin())
.pipe(gulp.dest(images.out));
});

gulp.task('fonts', function() {
return gulp.src(fonts.in)
.pipe(newer(fonts.out))
.pipe(gulp.dest(fonts.out));
});

gulp.task('sass', function() {
return gulp.src(css.in)

	.pipe(sass(css.sassOpts))
    
    .pipe(size({title: 'CSS in '}))
    .pipe(pleeease(css.pleeeaseOpts))
    .pipe(size({title: 'CSS out '}))
    
.pipe(gulp.dest(css.out))
    .pipe(browserSync.stream());

});

gulp.task('js', function(){
if(devBuild) {
return gulp.src(js.in)
.pipe(newer(js.out))
.pipe(jshint())
.pipe(jshint.reporter('default'))
.pipe(jshint.reporter('fail'))
.pipe(gulp.dest(js.out));
}
else {
del([
dest + 'js/*'
]);
return gulp.src(js.in)
.pipe(deporder())
.pipe(concat(js.filename))
.pipe(size({title: 'JS in'}))
.pipe(stripdebug())
.pipe(uglify())
.pipe(size({title: 'JS Out'}))
.pipe(gulp.dest(js.out));
}
});

gulp.task('browserSync', function(){
browserSync(syncOpts);
});

gulp.task('default', ['html', 'images', 'fonts', 'sass', 'js', 'browserSync'],
function() {

gulp.watch(html.watch, ['html',  browserSync.reload]);

gulp.watch(images.in, ['images']);


gulp.watch(fonts.in, ['fonts']);


gulp.watch([css.watch], ['sass']);


gulp.watch(js.in,['js',  browserSync.reload]);

});
`