noun
empty state; nil state
Computing term for a state containing no data or a null value.
変数が空状態のときは、デフォルト値が使われる。
When the variable is in an empty state, the default value is used.
状態 means 'state' or 'condition' in general; 空状態 specifically refers to an empty or nil state in computing.
Compound of 空 (くう, 'empty') and 状態 (じょうたい, 'state'), likely a calque from English computing terminology.