fix: use isinstance for proper type narrowing in Knowledge.query

Co-Authored-By: Joe Moura <joao@crewai.com>

src/crewai/knowledge/knowledge.py

@@ -49,9 +49,15 @@ class Knowledge(BaseModel):
         """
         Query across all knowledge sources to find the most relevant information.
         Returns the top_k most relevant chunks.
-        """
 
-        results = self.storage.search(
+        Raises:
+            ValueError: If no storage is configured for querying.
+        """
+        storage = self.storage
+        if not isinstance(storage, KnowledgeStorage):
+            raise ValueError("No storage found to perform query.")
+        # Using isinstance check for proper type narrowing
+        results = storage.search(
             query,
             limit,
         )