[FIX] website: not fail when no dynamic filter is defined

Since [1] when only website is installed, dropping a dynamic snippet
produces an error because no dynamic filter is defined and it tries to
specify one selected by default.

This commit avoids setting a default filter when there is none.

It did work in 15.0 because the log was inside
`_renderDynamicFiltersSelector` which contained an
`if (dynamicFilters.length > 0)` that avoided the problem.
In [2], when most of that logic was moved from the render method to the
fetch method, that condition was lost.

Steps to reproduce:
- Install website only
- Go to debug mode
- Drop a "Dynamic Snippet" or a "Dynamic Carousel"
=> Traceback appears because there cannot be a default filter when there
is no filter.

[1]: https://github.com/odoo/odoo/commit/3355dc16235355fe51e894f14e275210464608c6
[2]: https://github.com/odoo/odoo/commit/9e0b398fe608e716835260c5f9923f933d723f8e

opw-3166634

closes odoo/odoo#114068

X-original-commit: 8e23f08b1470ec5fe47a4459c4d3a8ad314c43b0
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/website/static/src/snippets/s_dynamic_snippet/options.js

@@ -154,6 +154,10 @@ const dynamicSnippetOptions = options.Class.extend({
             model_name: this.modelNameFilter,
             search_domain: this.contextualFilterDomain,
         }});
+        if (!dynamicFilters.length) {
+            // Additional modules are needed for dynamic filters to be defined.
+            return;
+        }
         for (let index in dynamicFilters) {
             this.dynamicFilters[dynamicFilters[index].id] = dynamicFilters[index];
         }