Require at least one category when setting article categories

Prevents articles from becoming unreachable by rejecting empty
categoryIds arrays in setCategoryIdsBySku.

src/store/article/setCategoryIdsBySku.js

@@ -25,6 +25,9 @@ export default function setCategoryIdsBySku(pool) {
       seen.add(categoryId);
       normalized.push(categoryId);
     }
+    if (normalized.length === 0) {
+      throw new Error('Article must have at least one category');
+    }
 
     const { articleId, languageId, companyId } = await resolve(
       googleAuthId,