Fix issue with instanceof

`image instanceof ImageModel` does not seem to be 100% safe, it works
when ipycanvas is installed locally but does not work in the pypi
package

Author: martinRenou

package.json

@@ -44,7 +44,6 @@
   },
   "dependencies": {
     "@jupyter-widgets/base": "^2.0.1",
-    "@jupyter-widgets/controls": "^1.5.2",
     "lodash": ">=4.17.13"
   },
   "devDependencies": {

src/widget.ts

@@ -5,10 +5,6 @@ import {
   DOMWidgetModel, DOMWidgetView, ISerializers, Dict, ViewList, unpack_models
 } from '@jupyter-widgets/base';
 
-import {
-  ImageModel
-} from '@jupyter-widgets/controls';
-
 import {
   MODULE_NAME, MODULE_VERSION
 } from './version';
@@ -194,7 +190,7 @@ class CanvasModel extends DOMWidgetModel {
       return;
     }
 
-    if (image instanceof ImageModel) {
+    if (image.get('_model_name') == 'ImageModel') {
       // Create the image manually instead of creating an ImageView
       let url: string;
       const format = image.get('format');