while using webtest to test our portal we get an JavaScript-Error.

JavaScript error loading page https://fachportal.key-work-asp.de/ags_demo/ofbiz/articleProjection/control/EditArticleSizeAllocation?apnDispoDatasetId=205&articleId=ART_10020: TypeError: Cannot find function getContext in object [object]. (https://fachportal.key-work-asp.de/ags_demo/js/bluff/bluff-src.js#2101)

caused by this JavaScript-snippet:

Bluff.Renderer = new JS.Class({
extend: {
WRAPPER_CLASS: 'bluff-wrapper',
TEXT_CLASS: 'bluff-text'
},

font: 'Arial, Helvetica, Verdana, sans-serif',
gravity: 'north',

initialize: function(canvasId) {
this._canvas = document.getElementById(canvasId);
this._ctx = this._canvas.getContext('2d');
},

scale: function(sx, sy) {
this._sx = sx;
this._sy = sy || sx;
},
........

Thanks for your gorgeous work!