gulp.task('scripts', function () {
return gulp.src([
    'app/js/libs/jquery.magnific-popup.min.js',
    'app/js/libs/slick.min.js',
    'app/js/common.js'
])
.pipe(concat('main.min.js'))
.pipe(uglify())
.pipe(gulp.dest('dist/js'));
});

var plumber = require('gulp-plumber');

gulp.task('scripts', () => {
  return gulp.src('app/scripts')
  .pipe(plumber())
  // весь остальной код таска
});