title: Gulp-less watcher breaks when a less error is encountered in a file
body: <p>I want to watch a folder of less files. When one of them is changed, i want to compile only the "styles.less" file (this file contains @imports to the rest of the files like "header.less", "navigation.less", etc.) 
  For this, i created 2 tasks.When i run the task "watchless", everything is ok, it compiles the styles.less to styles.css. But if an error is ecountered, when i edit a less file, the watcher breaks, even with gulp-plumber. How can i fix this?</p>
  
  <pre><code>var gulp = require('gulp');
  var plumber = require('gulp-plumber');
  var less = require('gulp-less');
  var watch = require('gulp-watch');
  
  var path_less = 'templates/responsive/css/less/';
  var path_css = 'templates/responsive/css/';
  
  gulp.task('less2css', function () {
      return gulp.src(path_less + 'styles.less')
          .pipe(plumber())
          .pipe(less())
          .pipe(gulp.dest(path_css))
  });
  
  gulp.task('watchless', function() {
     gulp.watch(path_less + '*.less', ['less2css']);  // Watch all the .less files, then run the less task
  });
  </code></pre>