fix(spa): handle empty category and products in carousel block

Render the products carousel block gracefully when category_id is
missing or when the selected category has no products, instead of
throwing Vue Router's "Missing required param 'category_id'" error.

frontend/spa/src/components/MainPage/Blocks/ProductsCarouselBlock.vue

@@ -2,10 +2,23 @@
   <BaseBlock
     :title="block.title"
     :description="block.description"
-    :moreLink="{name: 'product.categories.show', params: { category_id: block.data.category_id }}"
+    :moreLink="hasCategory ? {name: 'product.categories.show', params: { category_id: block.data.category_id }} : null"
     :moreText="block.data.all_text"
   >
+    <div v-if="!hasCategory" role="alert" class="alert alert-warning alert-soft">
+      <svg xmlns="http://www.w3.org/2000/svg" class="h-6 w-6 shrink-0 stroke-current" fill="none" viewBox="0 0 24 24">
+        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z" />
+      </svg>
+      <span>Для блока не выбрана категория.</span>
+    </div>
+    <div v-else-if="!hasProducts" role="alert" class="alert alert-soft">
+      <svg xmlns="http://www.w3.org/2000/svg" class="h-6 w-6 shrink-0 stroke-current" fill="none" viewBox="0 0 24 24">
+        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
+      </svg>
+      <span>В этой категории пока нет товаров.</span>
+    </div>
     <Swiper
+        v-else
         class="select-none block-products-carousel"
         :slides-per-view="block.data?.carousel?.slides_per_view || 2.5"
         :space-between="block.data?.carousel?.space_between || 20"
@@ -36,6 +49,7 @@
 </template>
 
 <script setup>
+import {computed} from "vue";
 import {useYaMetrikaStore} from "@/stores/yaMetrikaStore.js";
 import {Swiper, SwiperSlide} from "swiper/vue";
 import {useHapticScroll} from "@/composables/useHapticScroll.js";
@@ -52,6 +66,9 @@ const props = defineProps({
   }
 });
 
+const hasCategory = computed(() => Boolean(props.block.data?.category_id));
+const hasProducts = computed(() => (props.block.data?.products?.data?.length ?? 0) > 0);
+
 const freeModeSettings = {
   enabled: props.block.data?.carousel?.freemode?.enabled || false,
 };