fix: ignore empty outputs in Tool node (#10988)

api/core/workflow/nodes/tool/tool_node.py

@@ -250,9 +250,8 @@ class ToolNode(BaseNode[ToolNodeData]):
                 f"{message.message}"
                 if message.type == ToolInvokeMessage.MessageType.TEXT
                 else f"Link: {message.message}"
-                if message.type == ToolInvokeMessage.MessageType.LINK
-                else ""
                 for message in tool_response
+                if message.type in {ToolInvokeMessage.MessageType.TEXT, ToolInvokeMessage.MessageType.LINK}
             ]
         )