fix: 'validation error for ToolInvokeMessage' when blob_message meta is None (#11212)

api/core/tools/tool/tool.py

@@ -324,7 +324,12 @@ class Tool(BaseModel, ABC):
         :param blob: the blob
         :return: the blob message
         """
-        return ToolInvokeMessage(type=ToolInvokeMessage.MessageType.BLOB, message=blob, meta=meta, save_as=save_as)
+        return ToolInvokeMessage(
+            type=ToolInvokeMessage.MessageType.BLOB,
+            message=blob,
+            meta=meta or {},
+            save_as=save_as,
+        )
 
     def create_json_message(self, object: dict) -> ToolInvokeMessage:
         """