Fix GET arguments encoding

static/canvas.js

@@ -22,7 +22,7 @@ let params = {};
 if (window.location.search) {
   let splitParams = window.location.search.split('?')[1].split('&');
   for (let i in splitParams) {
-    params[splitParams[i].split('=')[0]] = decodeURIComponent(splitParams[i].split('=')[1]);
+    params[splitParams[i].split('=')[0]] = decodeURIComponent(splitParams[i].split('=')[1]).replace(/\+/g, ' ');
   }
 }