prevent source errors from crashing gulp watch

gulpfile.js

@@ -2,11 +2,18 @@
 const gulp = require('gulp');
 const less = require('gulp-less');
 
+function swallowError(error) {
+	console.log(error.toString())
+
+	this.emit('end')
+}
+
 gulp.task('less', function(cb) {
   gulp
     .src(['themes/compact.less', 'themes/compact_night.less',
          'themes/light.less', 'themes/night_blue.less', 'themes/night.less'])
     .pipe(less())
+    .on('error', swallowError)
     .pipe(
       gulp.dest(function(f) {
         return f.base;