[FIX] web_editor: prevent crash if data-shape-colors is not set

There is cases leading to have a `data-shape` but no
`data-shape-colors`. It then makes the code crash.

Step to reproduce:
- Drag & drop "Text - Image" snippet
- Double click on an image to replace it
- Select in the media dialog "Add URL" and insert a CORS protected
  image URL
- The image is correctly added, and its url is something like
  `/web/image/123-redirect/xxx.jpg`
- Click on the image and then click on its "Animation" option
-> It crashes

In such a case, the code was crashing on the line below this fix:
`img.dataset.shapeColors.split(';')`

The modified code here is related to commit [1].
But the code only break in Odoo 17, probably following commit [2].

[1]: https://github.com/odoo/odoo/commit/cd403480f90cf7103651f3be818a14b06d3c73ca
[2]: https://github.com/odoo/odoo/commit/7f730f81ec541cc7791fc6b3fded17c838433f85

Part-of: odoo/odoo#146732

addons/web_editor/static/src/js/editor/snippets.options.js

@@ -7002,7 +7002,8 @@ registry.ImageTools = ImageHandlerOption.extend({
         if (widgetName.startsWith('img-shape-color')) {
             const img = this._getImg();
             const shapeName = img.dataset.shape;
-            if (!shapeName) {
+            const shapeColors = img.dataset.shapeColors;
+            if (!shapeName || !shapeColors) {
                 return false;
             }
             const colors = img.dataset.shapeColors.split(';');