Why it doesn't filter as I expected

Hello all,

I created a card from the dataset. The card setting is as follows. When I filtered "Card Title" to be equal to "null" by QuickFilter, the count of action is expected to be 2. But actually The count of action shows 0. What was wrong?

Chart type = Bar
X AXIS = Name
Y AXIS = Count of Action
SERES = Page name
Quick Filter = Page name, Card Title

Japanese--

このようなデータセットが存在します。下記の設定でCardを作成しました。
Chart type = Bar
X AXIS = Name
Y AXIS = Count of Action
SERES = Page name
Quick Filter = Page name, Card Title

Quick filterでCard Title = null　を選択したら、Count of action = 2 になってほしいですが、実際は０ count of action　になってしまいます。
何が悪いのでしょうか？よろしくお願いいたします。