Fixed issues with references and checks

Author: Deep Dave

src/plugin/pagebreaks.js

@@ -1,5 +1,5 @@
 import Worker from '../worker.js';
-import { objType, createElement } from './utils.js';
+import { objType, createElement } from '../utils.js';
 
 // Add page-break functionality.
 
@@ -33,9 +33,10 @@ Worker.prototype.toContainer = function toContainer() {
 
     // Get arrays of all explicitly requested elements.
     var select = {};
+    var self = this;
     ['before', 'after', 'avoid'].forEach(function(key) {
       var all = mode.avoidAll && key === 'avoid';
-      select[key] = all ? [] : [].concat(this.opt.pageBreak[key]);
+      select[key] = all ? [] : (undefined === self.opt.pageBreak[key] ? [] : [].concat(self.opt.pageBreak[key]));
       if (select[key].length > 0) {
         select[key] = Array.prototype.slice.call(
           root.querySelectorAll(select[key].join(', ')));