randomly slide the canvas

1 files changed, 2 insertions, 1 deletions

diff --git a/js/matrix.js b/js/matrix.js
index de59e17..1aeb929 100644
--- a/js/matrix.js
+++ b/js/matrix.js
@@ -58,7 +58,7 @@ Matrix.prototype.demolish = function (){
   this.forEach(function(lex){
     lex.demolish()
   })
-  while (this.rapper.firstChild) {
+  while (this.rapper && this.rapper.firstChild) {
     this.rapper.removeChild(this.rapper.firstChild);
   }
   this.aa.forEach(function(row){
@@ -124,6 +124,7 @@ Matrix.prototype.build = function(){
 }
 Matrix.prototype.append = function(rapper){
   rapper = this.rapper = rapper || this.rapper
+  if (! this.rapper) return
   this.aa.forEach(function(row, y){
     var div = document.createElement("div")
     row.forEach(function(lex, x) {