Added getScopeCacheKey in order to validate the store ID and return t…

…he right cache key

app/code/Magento/Catalog/Model/CategoryRepository.php

@@ -9,8 +9,10 @@
 
 use Magento\Framework\Exception\CouldNotSaveException;
 use Magento\Framework\Exception\NoSuchEntityException;
+use Magento\Framework\Exception\SerializationException;
 use Magento\Framework\Exception\StateException;
 use Magento\Catalog\Api\Data\CategoryInterface;
+use Magento\Framework\Phrase;
 
 /**
  * Repository for categories.
@@ -128,10 +130,11 @@ public function save(\Magento\Catalog\Api\Data\CategoryInterface $category)
 
     /**
      * @inheritdoc
+     * @throws SerializationException
      */
     public function get($categoryId, $storeId = null)
     {
-        $cacheKey = $storeId ?? 'all';
+        $cacheKey = $this->getScopeCacheKey($storeId);
         if (!isset($this->instances[$categoryId][$cacheKey])) {
             /** @var Category $category */
             $category = $this->categoryFactory->create();
@@ -238,4 +241,26 @@ private function getMetadataPool()
         }
         return $this->metadataPool;
     }
+
+    /**
+     * Returns a cache key based on scope
+     *
+     * @param string|integer|null $storeId
+     *
+     * @throws SerializationException
+     * @return integer
+     */
+    private function getScopeCacheKey($storeId = null)
+    {
+        if (null !== $storeId && !is_numeric($storeId)) {
+            throw new SerializationException(
+                new Phrase(
+                    'The "%value" value\'s type is invalid. The "%type" type was expected. '
+                    . 'Verify and try again.',
+                    ['value' => $storeId, 'type' => 'int']
+                )
+            );
+        }
+        return $storeId ?? 'all';
+    }
 }