add possibility to handle camera unavailability

		zk.afterLoad('zkmax.med', function() {
			var xCamera = {};
			zk.override(zkmax.med.Camera.prototype, xCamera, {
				requestCamera : function(callback, handleError) { //second optional parameter allows customization when calling the requestCamera
					var wgt = this,
						video = this.$n('real'),
						constraints = this.getConstraints() || {audio: this._audio, video: true};

					navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia ||
									navigator.mozGetUserMedia || navigator.msGetUserMedia ||
									navigator.oGetUserMedia || navigator.mediaDevices.getUserMedia;

					navigator.getUserMedia(constraints,
						function (stream) {
							if (callback) {
								window.setTimeout(function () {
									callback();
								}, 500);
							}
							wgt._settingPreview(wgt._previewRecord);
							video.srcObject = stream;
						},
						handleError || this.handleCameraUnavailable;
					);
				},

				//widget method allowing to override globally
				handleCameraUnavailable: function(error) {
					this.fire('onCameraUnavailable', {error: error});
				}
			});//zk.override
		});//zk.afterLoad